Lecture Xxviii

ARTIFICIAL AND NATURAL SELECTION

The comparison of artificial and natural selection has furnished material support for the theory of descent, and in turn been the object of constant criticism since the time of Darwin. The criticisms, in greater part, have arisen chiefly from an imperfect knowledge of both processes. By the aid of distinctions recently made possible, the contrast between elementary species and improved races has become much more vivid, and promises to yield better results on which to base comparisons of artificial and natural selection.

Elementary species, as we have seen in earlier lectures, occur in wild and in cultivated plants. In older genera and systematic species they are often present in small numbers only, but many of the more recent wild types and also many of the cultivated forms are very rich in this respect. In agriculture the choice of the most adequate elementary forms for any special purpose is acknowledged as the first step in the way of selection, and is designated by the name of variety-testing, applying the term variety to all the subdivisions of systematic species indiscriminately. In natural processes it bears the title of survival of species. The fact that recent types show large numbers, and in some instances even hundreds of minor constant forms, while the older genera are considerably reduced in this respect, is commonly explained by the assumption of extinction of species on a correspondingly large scale. This extinction is considered to affect the unfit in a higher measure than the fit. Consequently the former vanish, often without leaving any trace of their existence, and only those that prove to be sufficiently adapted to the surrounding external conditions, resist and survive.

This selection exhibits far-reaching analogies between the artificial and the natural processes, and is in both cases of the very highest importance. In nature the dying out of unfit mutations is the result of the great struggle for life. In a previous lecture we have compared its agency with that of a sieve. All elements which are too small or too weak fall through, and only those are preserved which resist the sifting process. Reduced in number they thrive and multiply and are thus enabled to strike out new mutative changes. These are again submitted to the sifting tests, and the frequent repetition of this process is considered to give a good explanation of the manifold, highly complicated, and admirable structures which strike the beginner as the only real adaptations in nature.

Exactly in the same way artificial selection isolates and preserves some elementary species, while it destroys others. Of course the time is not sufficient to secure new mutations, or at least these are only rare at present, and their occurrence is doubtful in historic periods. Apart from this unavoidable difference the analogy between natural and artificial selection appears to me to be very striking.

This form of selection may be termed selection between species. Opposed to it stands the selection within the elementary species or variety. It has of late, alone come to be known as selection, though in reality it does not deserve this distinction. I have already detailed the historical evidence which gives preference to selection between species. The process can best be designated by the name of intraspecific selection, if it is understood that the term intraspecific is meant to apply to the conception of small or elementary species.

I do not wish to propose new terms, but I think that the principal differences might better become understood by the introduction of the word election into the discussion of questions of heredity. Election meant formerly the preferential choice of single individuals, while the derivation of the word selection points to a segregation of assemblies into their larger parts. Or to state it in a shorter way, individual selection is exactly what is usually termed election. Choosing one man from among thousands is to elect him, but a select party is a group of chosen persons. There would be no great difficulty in the introduction of the word election, as breeders are already in the habit of calling their choice individuals "elite," at least in the case of beets and of cereals.

This intraspecific selection affords a second point for the comparison between natural and artificial processes. This case is readily granted to be more difficult than the first, but there can be no doubt that the similarity is due to strictly comparable causes. In practice this process is scarcely second in importance to the selection between species, and in numerous cases it rests upon it, and crowns it, bringing the isolated forms up to their highest possible degree of usefulness. In nature it does quite the same, adapting strains of individuals to the local conditions of their environment. Improved races do not generally last very long in practice; sooner or later they are surpassed by new selections. Exactly so we may imagine the agency of natural intraspecific selection. It produces the local races, the marks of which disappear as soon as the special external conditions cease to act. It is responsible only for the smallest lateral branches of the pedigree, but has nothing in common with the evolution on the main stems. It is of very subordinate importance.

These assertions of course, are directly opposed to the current run of scientific belief, but they are supported by facts. A considerable part of the evidence has already been dealt with and for our closing discussion only an exact comparison remains to be made between the two detailed types of intraspecific selection. In coming to this I will first dwell upon some intermediate types and conclude with a critical discussion of the features of artificial selection, which to my mind prove the invalidity of the conclusions drawn from it in behalf of an explanation of the processes of nature.

Natural selection occurs not only in the wild state, but is also active in cultivated fields. Here it regulates the struggle of the selected varieties and improved races with the older types, and even with the wild species. In a previous lecture I have detailed the rapid increase of the wild oats in certain years, and described the experiments of Risler and Rimpau in the running out of select varieties. The agency is always the same. The preferred forms, which give a larger harvest, are generally more sensitive to injurious influences, more dependent on rich manure and on adequate treatment. The native varieties have therefore the advantage, when climatic or cultural conditions are unfavorable for the fields at large. They suffer in a minor degree, and are thereby enabled to propagate themselves afterwards more rapidly and to defeat the finer types. This struggle for life is a constant one, and can easily be followed, whenever the composition of a strain is noted in successive years. It is well appreciated by breeders and farmers, because it is always liable to counteract their endeavors and to claim their utmost efforts to keep their races pure. There can be no doubt that exactly the same struggle exempt from man's intrusion is fought out in the wild state.

Local races of wild plants have not been the object for field observations recently. Some facts however, are known concerning them. On the East Friesian Islands in the North Sea the flowers are strikingly larger and brighter colored than those of the same species on the neighboring continent. This local difference is ascribed by Behrens to a more severe selection by the pollinating insects in consequence of their lesser frequency on these very windy isles. Seeds of the pines from the Himalayas yield cold-resisting young plants if gathered from trees in a high altitude, while the seeds of the same species from lower regions yield more sensitive seedlings. Similar instances are afforded by Rhododendron and other mountain species. According to Cieslar corresponding differences are shown by seeds of firs and larches from alpine and lowland provinces.

Such changes are directly dependent on external influences. This is especially manifest in experiments extending the cultures in higher or in more northern regions. The shorter summer is a natural agent of selection; it excludes all individuals which cannot ripen their seeds during so short a period. Only the short lived ones survive. Schubeler made very striking experiments with corn and other different cereals, and has succeeded in making their culture possible in regions of Norway where it formerly failed. In the district of Christiania, corn had within some few years reduced its lifetime from 123 to 90 days, yielding smaller stems and fewer kernels, but still sufficient to make its culture profitable under the existing conditions. This change was not permanent, but was observed to diminish rapidly and to disappear entirely, whenever the Norwegian strain was cultivated in the southern part of Germany. It was a typical improved race, dependent on continual selection by the short summers which had produced it. Similar results have been reached by Von Wettstein in the comparison of kinds of flax from different countries. The analogy between such cultivated local races and the local races of nature is quite striking. The practice of seed exchange rests for a large part on the experience that the characters, acquired under the definite climatic and cultural conditions of some select regions, hold good for one or two, and sometimes even more generations, before they decrease to practical uselessness. The Probstei, the Hanna and other districts owe their wealth to this temporary superiority of their wheat and other cereals.

Leaving these intermediate forms of selection, we now come to our principal point. It has already been discussed at some length in the previous lecture, but needs further consideration. It is the question whether intraspecific selection may be regarded as a cause of lasting and ever-increasing improvement. This is assumed by biologists who consider fluctuating variability as the main source of progression in the organic world. But the experience of the breeders does not support this view, since the results of practice prove that selection according to a constant standard soon reaches a limit which it is not capable of transgressing. In order to attain further improvements the method of selection itself must be improved. A better and sharper method assures the choice of more valuable representatives of the race, even if these must be sought for in far larger numbers of individuals, as is indicated by the law of Quetelet.

Continuous or even prolonged improvement of a cultivated race is not the result of frequently repeated selection, but of the improvement of the standard of appreciation. Nature, as far as we know, changes her standard from time to time only in consequence of the migrations of the species, or of local changes of climate. Afterwards the new standard remains unchanged for centuries.

Selection, according to a constant standard, reaches its results in few generations. The experience of Van Mons and other breeders of apples shows that the limit of size and lusciousness may be soon attained. Vilmorin's experiments with wild carrots and those of Carriere with radishes lead to the same conclusion as regards roots. Improvements of flowers in size and color are usually easy and rapid in the beginning, but an impassable limit is soon reached. Numerous other instances could be given.

Contrasted with these simple cases is the method of selecting sugar beets. More than once I have alluded to this splendid example of the influence of man upon domestic races, and tried to point out how little support it affords to the current scientific opinion concerning the power of natural selection. For this reason it is interesting to see how a gradual development of the methods of selection has been, from the very outset, one of the chief aims of the breeders. None of them doubts that an improvement of the method alone is adequate to obtain results. This result, in the main, is the securing of a few percent more of sugar, a change hardly comparable with that progress in evolution, which our theories are destined to explain.

Vilmorin's original method was a very simple one. Polarization was still undiscovered in his time. He determined the specific weight of his beets, either by weighing them as a whole, or by using a piece cut from the base of the roots and deprived of its bark, in order to test only the sugar tissues. The pieces were floated in solutions of salt, which were diluted until the pieces began to sink. Their specific weight at that moment was determined and considered to be a measure of the corresponding value of the beet. This principle was afterwards improved in two ways. The first was a selection after the salt solution method, but performed on a large scale. After some few determinations, a solution was made of such strength as to allow the greater number of the beets to float, and only the best to sink down. In large vessels thousands of beets could be tested in this way, to select a few of the very heaviest. The other improvement was the determination of the specific weight of the sap, pressed out from the tissue. It was more tedious and more expensive, but more direct, as the influence of the air cavities of the tissue was excluded. It prepared the way for polarization.

This was introduced about the year 1874 in Germany, and soon became generally accepted. It allowed the amount of sugar to be measured directly, and with but slight trouble. Thousands of beets could be tested yearly by this method, and the best selected for the production of seed. In some factories a standard percentage is determined by previous inquiries, and the mass of the beets is tested only by it. In others the methods of taking samples and clearing the sap have been improved so far as to allow the exact determination of three hundred thousand polarization values of beets within a few weeks. Such figures give the richest material for statistical studies, and at once indicate the best roots, while they enable the breeder to change his standard in accordance with the results at any time. Furthermore they allow the mass of the beets to be divided into groups of different quality, and to produce, besides the seeds for the continuation of the race, a first class and second-class product and so on. In the factory of Messrs. Kuhn & Co., at Naarden, Holland, the grinding machine has been markedly improved, so as to tear all cell walls asunder, open all cells, and secure the whole of the sap within less than a minute, and without heating.

It would take too long to go into further details, or to describe the simultaneous changes that have been applied to the culture of the elite strains. The detailed features suffice to show that the chief care of the breeder in this case is a continuous amelioration of the method of selecting. It is manifest that the progression of the race is in the main due to great technical improvements, and not solely to the repetition of the selection.

Similar facts may be seen on all the great lines of industrial selection. An increasing appreciation of all the qualities of the selected plants is the common feature. Morphological characters, and the capacity of yielding the desired products, are the first points that strike the breeder. The relation to climate and the dependence on manure soon follow; but the physiological and chemical sides of the problem are usually slow of recognition in the methods of selection. When visiting Mr. de Vilmorin at Paris some years ago, I inspected his laboratory for the selection of potatoes. In the method in use, the tubers were rubbed to pulp and the starch was extracted and measured. A starch percentage figure was determined for each plant, and the selection of the tubers for planting was founded upon this result. In the same way wheat has been selected by Dippe at Quedlinburg, first by a determination of its nitrogenous contents in general, and secondly by the amount of the substances which determine its value for baking purposes.

The celebrated rye of Schlanstedt was produced by the late Mr. Rimpau in a similar manner and was put on the market between 1880 and 1890 and was received with great favor throughout central Europe, especially in Germany and in France. It is a tall variety, with vigorous stems and very long heads, the kernels of which are nearly double the size of those of the ordinary rye, and are seen protruding, when ripe, from between the scales of the spikelets. It is unfit for poor soils, but is one of the very best varieties for soils of medium fertility in a temperate climate. It is equal in the production of grain to the best French sorts, but far surpassing them in its amount of straw. It was perfected at the farm of Schlanstedt very slowly, according to the current conceptions of the period. The experiment was started in the year 1866, at which time Rimpau collected the most beautiful heads from among his fields, and sowed their kernels in his experiment garden. From this first culture the whole race was derived. Every year the best ears of the strain were chosen for repeated culture, under experimental care, while the remainder was multiplied in a field to furnish the seeds for large and continually increasing areas of his farms.

Two or three years were required to produce the quantity of seed of each kind required for all the fields of Schlanstedt. The experiment garden, which through the kindness of Mr. Rimpau I had the good fortune of visiting more than once between 1875 and 1878, was situated in the middle of his farm, at some distance from the dwellings. Of course it was treated with more care, and especially kept in better conditions of fertility than was possible for the fields at large. A continued study of the qualities and exigencies of the elite plants accompanied this selection, and gave the means of gradually increasing the standard. Resistance against disease was observed and other qualities were ameliorated in the same manner. Mr. Rimpau repeatedly told me that he was most anxious not to overlook any single character, because he feared that if any of them might become selected in the wrong way, perchance unconsciously, the whole strain might suffer to such a degree as to make all the other ameliorations quite useless. With this purpose the number of plants per acre was kept nearly the same as those in the fields, and the size of the culture was large enough every year to include the best kernels of quite a number of heads. These were never separated, and exact individual pedigrees were not included in the plan. This mixture seemed to have the advantage of keeping up an average value of the larger number of the characters, which either from their nature or from their apparent unimportance had necessarily to be neglected.

After ten years of continuous labor, the rye of Rimpau caught the attention of his neighbors, being manifestly better than that of ordinary sowings. Originally he had made his cultures for the improvement of his own fields only. Gradually however, he began to sell his product as seed to others, though he found the difference still very slight. After ten years more, about 1886, he was able to sell all his rye as seed, thereby making of course large profits. It is now acknowledged as one of the best sorts, though in his last letter Mr. Rimpau announced to me that the profits began to decline as other selected varieties of rye became known. The limit of productiveness was reached, and to surmount this, selection had to be begun again from some new and better starting point.

This new starting point invokes quite another principle of selection, a principle which threatens to make the contrast between artificial and natural selection still greater. In fact it is nothing new, being in use formerly in the selection of domestic animals, and having been applied by Vilmorin to his sugar beets more than half a century ago. Why it should ever have been overlooked and neglected in the selection of sugar beets now is not clear.

The principle in itself is very simple. It agrees that the visible characters of an animal or a plant are only an imperfect measure for its hereditary qualities, instead of being the real criterion to be relied upon, as is the current belief. It further reasons that a direct appreciation of the capacity of inheritance can only be derived from the observation of the inheritance itself. Hence it concludes that the average value of the offspring is the only real standard by which to judge the representatives of a race and to found selection upon.

These statements are so directly opposed to views prevalent among plant breeders, that it seems necessary to deal with them from the theoretical and experimental, as well as from the practical side.

The theoretical arguments rest on the division of the fluctuating variability into the two large classes of individual or embryonic, and of partial deviations. We have dealt with this division at some length in the previous lecture. It will be apparent at once, if we choose a definite example. Let us ask what is the real significance of the percentage figure of a single plant in sugar beets. This value depends in the first place, on the strain or family from which the beet has been derived, but this primary point may be neglected here, because it is the same for all the beets of any lot, and determines the average, around which all are fluctuating.

The deviation of the percentage figure of a single beet depends on two main groups of external causes. First come those that have influenced the young germs of the plant during its most sensitive period, when still an embryo within the ripening seed. They give a new limitation to the average condition, which once and forever becomes fixed for this special individual. In the second place the young seedling is affected during the development of its crown of leaves, and of its roots, by numerous factors, which cannot change this average, but may induce deviations from it, increasing or decreasing the amount of sugar, which will eventually be laid down in the root. The best young beet may be injured in many ways during periods of its lifetime, and produce less sugar than could reasonably be expected from it. It may be surpassed by beets of inferior constitution, but growing under more favorable circumstances.

Considered from this point of view the result of the polarization test is not a single value, but consists of at least two different factors. It may be equal to the algebraic sum of these, or to their difference, according to whether the external conditions on the field were locally and individually favorable or unfavorable. A large amount of sugar may be due to high individual value, with slight subsequent deviation from it, or to a less prominent character combined with an extreme subordinate deviation.

Hence it is manifest that even the results of such a highly improved technical method do not deserve the confidence usually put in them. They are open to doubt, and the highest figures do not really indicate the best representatives of the race. In order to convey this conception to you in a still stronger manner, let us consider the partial variability as it usually shows itself. The various leaves of a plant may noticeably vary in size, the flowers in color, the fruits in flavor. They fluctuate around an average, which is assumed to represent the approximate value of the whole plant. But if we were allowed to measure only one leaf, or to estimate only one flower or fruit, and be compelled to conclude from it the worth of the whole plant, what mistakes we could make! We might indeed hit upon an average case, but we might as easily get an extreme, either in the way of increase or of decrease. In both cases our judgment would be badly founded. Now who can assure us that the single root of a given beet is an average representative of the partial variability? The fact that there is only one main root does not prove anything. An annual plant has only one stem, but a perennial species has many. The average height of the last is a reliable character, but the casual height of the former is very uncertain.

So it is with the beets. A beet may be divided by its buds and give quite a number of roots, belonging to the same individual. These secondary roots have been tested for the amount of sugar, and found to exhibit a manifest degree of variability. If the first root corresponded to their average, it might be considered as reliable, but if not anyone will grant that an average is more reliable than a single determination. Deviations have as a fact been observed, proving the validity of our assertion. These considerations at once explain the disappointment so often experienced by breeders. Some facts may be quoted from the Belgian professor of agriculture at Gembloux, the late Mr. Laurent. He selected two beets, from a strain, with the exceptional amount of 23% sugar, but kept their offspring separate and analyzed some 60 of each. In both groups the average was only 11-12%, the extremes not surpassing 14-15%. Evidently the choice was a bad one, notwithstanding the high polarization value of the parent. Analogous cases are often observed, and my countrymen, Messrs. Kuhn & Co., go so far as to doubt all excessive variants, and to prefer beets with high, but less extraordinary percentages. Such are to be had in larger numbers and their average has a good chance of exemption from a considerable portion of the doubts adhering to single excessive cases.

It is curious to note here what Louis de Vilmorin taught concerning this point in the year 1850. I quote his own words: "I have observed that in experiments on heredity it is necessary to individualize as much as possible. So I have taken to the habit of saving and sowing separately the seeds of every individual beet, and I have always found that among the chosen parent plants some had an offspring with a better average yield than others. At the end I have come to consider this character only, as a standard for amelioration."

The words are clear and their author is the originator of the whole method of plant breeding selection. Yet the principle has been abandoned, and nearly forgotten under the impression that polarization alone was the supreme guide to be relied upon. However, if I understand the signs rightly, the time is soon coming when Vilmorin's experience will become once more the foundation for progress in breeding.

Leaving the theoretical and historical aspects of the problem, we will now recall the experimental evidence, given in a former lecture, dealing with the inheritance of monstrosities. I have shown that in many instances monstrosities constitute double races, consisting of monstrous and of normal individuals. At first sight one might be induced to surmise that the monstrous ones are the true representatives of the race, and that their seeds should be exclusively sown, in order to keep the strain up to its normal standard. One might even suppose that the normal individuals, or the so-called atavists, had really reverted to the original type of the species and that their progeny would remain true to this.

My experiments, however, have shown that quite the contrary is the case. No doubt, the seeds of the monstrous specimens are trustworthy, but the seeds of the atavists are not less so. Fasciated hawkweeds and twisted teasels gave the same average constitution of the offspring from highly monstrous, and from apparently wholly normal individuals. In other words the fullest development of the visible characteristic was not in the slightest degree an indication of better hereditary tendencies. In unfavorable years a whole generation of a fasciated race may exhibit exclusively normal plants, without transmitting a trace of this deficiency to the following generation. As soon as the suitable conditions return, the monstrosity reassumes its full development. The accordance of these facts with the experience of breeders of domestic animals, and of Louis de Vilmorin, and with the result of the theoretical considerations concerning the factors of fluctuation has led me to suggest the method of selecting, which I have made use of in my experiments with tricotyls and syncotyls.

Seedling variations afford a means of counting many hundreds of individuals in a single germinating pan. If seed from one parent plant is sown only in each pan, a percentage figure for the amount of deviating seedlings may be obtained. These figures we have called the hereditary percentages. I have been able to select the parent plants after their death on the sole ground of these values. And the result has been that from varieties which, on an average, exhibited 50-55% deviating seedlings, after one or two years of selection this proportion in the offspring was brought up to about 90% in most of the cases. Phacelia and mercury with tricotylous seedlings, and the Russian sunflower with connate seed leaves, may be cited as instances.

Besides these tests, others were performed, based only on the visible characters of the seedlings. The result was that this characteristic was almost useless as a criterion. The atavists gave, in the main, nearly the same hereditary percentages as the tricotyls and syncotyls, and their extremes were in each case far better constituted than the average of the chosen type. Hence, for selection purposes, the atavists must be considered to be in no way inferior to the typical specimens.

If it had been possible to apply this principle to twisted and fasciated plants, and perhaps even to other monstrosities, I think that it will readily be granted that the chance of bringing even these races up to a percentage of 90% would have been large enough. But the large size of the cultures required for the counting of numerous groups of offspring in the adult state has deterred me from making such trials. Recently however, I have discovered a species, Viscaria oculata which allows of counting twisted specimens in the pans, and I may soon be able to obtain proofs of this assertion. The validity of the hereditary percentage as a standard of selection has, within the last few years, been recognized and defended by two eminent breeders, W.A. Hays in this country and Von Lochow in Germany. Both of them have started from the experience of breeders of domestic animals. Von Lochow applied the principle to rye. He first showed how fallacious the visible characters often are. For instance the size of the kernels is often dependent on their number in the head, and if this number is reduced by the injurious varietal mark of lacunae (Luckigkeit), the whole harvest will rapidly deteriorate by the selection of the largest kernels from varieties which are not quite free from this hereditary deficiency.

In order to estimate the value of his rye plants, he gathers the seed of each one separately and sows them in rows. Each row corresponds to a parent plant and receives 200 or 150 seeds, according to the available quantity. In this way from 700 to 800 parent plants are tested yearly. Each row is harvested separately. The number of plants gives the average measure of resistance to frost, this being the only important cause of loss. Then the yield in grain and straw is determined and calculated, and other qualities are taken into consideration. Finally one or more groups stand prominent above all others and are chosen for the continuation of the race. All other groups are wholly excluded from the "elite," but among them the best groups and the very best individuals from lesser groups are considered adequate for further cultivation, in order to produce the commercial product of the race.

As a matter of fact the rye of Von Lochow is now one of the best varieties, and even surpasses the celebrated variety of Schlanstedt. It was only after obtaining proof of the validity of his method that Von Lochow decided to give it to the public.

W.M. Hays has made experiments with wheat at the Minnesota Agricultural Experiment Station. He chose a hundred grains as a proper number for the appreciation of each parent plant, and hence has adopted the name of "centgener power" for the hereditary percentage.

The average of the hundred offspring is the standard to judge the parent by. Experience shows at once that this average is not at all proportional to the visible qualities of the parent. Hence the conclusion that the yield of the parent plant is a very uncertain indication of its value as a parent for the succeeding generation. Only the parents with the largest power in the centgener of offspring are chosen, while all others are wholly discarded. Afterwards the seeds of the chosen groups are propagated in the field until the required quantities of seed are obtained.

This centgener power, or breeding ability, is tested and compared for the various parent plants as to yield, grade, and percentage of nitrogenous content in the grain, and as to the ability of the plant to stand erect, resist rust, and other important qualities. It is evident that by this test of a hundred specimens a far better and much more reliable determination can be made than on the ground of the minutest examination of one single plant. From this point of view the method of Hays commands attention. But the chief advantage lies in the fact that it is a direct proof of that which it is desired to prove, while the visible marks give only very indirect information.

Thus the results of the men of practice are in full accordance with those of theory and scientific experiment, and there can be little doubt that they open the way for a rapid and important improvement. Once attained, progress however, will be dependent on the selection principle, and the hereditary percentage, or centgener power or breeding ability, must be determined in each generation anew. Without this the race would soon regress to its former condition.

To return to our starting point, the comparison of artificial and natural selection. Here we are at once struck by the fact that it is hardly imaginable, how nature can make use of this principle. In some measure the members of the best centgener will manifestly be at an advantage, because they contain more fit specimens than the other groups. But the struggle for existence goes on between individuals, and not between groups of brethren against groups of cousins. In every group the best adapted individuals will survive, and soon the breeding differences between the parents must vanish altogether. Manifestly they can, as a rule, have no lasting result on the issue of the struggle far existence.

If now we remember that in Darwin's time this principle, breeding ability, enjoyed a far more general appreciation than at present, and that Darwin must have given it full consideration, it becomes at once clear that this old, but recently revived principle, is not adequate to support the current comparison between artificial and natural selection.

In conclusion, summing up all our arguments, we may state that there is a broad analogy between breeding selection in the widest sense of the word, including variety testing, race improvement and the trial of the breeding ability on one side, and natural selection on the other. This analogy however, points to the importance of the selection between elementary species, and the very subordinate role of intraspecific selection in nature. It strongly supports our view of the origin of species by mutation instead of continuous selection. Or, to put it in the terms chosen lately by Mr. Arthur Harris in a friendly criticism of my views: "Natural selection may explain the survival of the fittest, but it cannot explain the arrival of the fittest."

Abies concolor fastigiata, 618 Acacia, 176, 196, 217, 458, 697 bastard, 343, 617, 618, 664, 665, 666 Acer compestre nanum, 612 Achillea millefolium, 131, 132, 441 Adaptation, 702 double, 430, 451, 452, 454, 455, 457, 458, 642 Aegilops ovata, 265 speltaeformis, 265 Agave vivipara, 684 Ageratum coeruleum, 612 Agrostemma Coronaries bicolor, 125 Githago, 282 nicaeensis, 162 Agrotis, 204 Alder, cut-leaved, 147, 596 Alfalfa, 264 Algae, 699 Allen, Grant, 237 Alliaria, 638 Alnus glutinosa laciniata, 615 Alpine plants, 437, 695, 794 Althaea, 490 Amaranth, 282, 452 Amaranthus caudatus, 282 Amaryllis, 272, 275, 762 brasiliensis, 275 leopoldi, 275 pardina, 275 psittacina, 275 vittata, 275 Amen-Hotep, 697 Ampelopsis, 239 Amygdalus persica laevis, 126 Anagallis arvensis, 162 Androsace, 634 Anemone, 266, 331 coronaria, 241, 491 var. "Bride," 510 magellanica, 266 sylvestris, 266 Anemone, garden, 241 Annee, 760 Anomalies, taxonomic, 658, 685 Anthemis, 236 nobilis, 130 Anthurium scherzerianum, 639 Antirrhinum majus, 315 luteum rubro-striatum, 315 Apetalous flowers, 622 Apples, 134, 240, 328, 454, 806 elementary species, 75 method of cultivating, 76 origin of cultivated varieties, 73 use by the Romans, 74 "Wealthy," 78, 79 wild, 73, 74, 75, 76 Aquilegia chrysantha, 161 Arabis ciliata glabrata hirsuta glaberrima, 126 Aralia crassifolia, 662 Arbres fruitiers ou Pomonomie belge, 76 Aralia papyrifera, 662 Arctic flora, 695 Arnica, 494 montana, 236 Aroids, 222, 631, 639 Artemisias, 131 Artificial selection, 18, 71, 77, 93, 95, 743, 744, 798, 826 first employed, 72, 92 nature of, 19 Arum maculatum immaculatum, 125 Ascidia, 310, 366, 367, 427, 428, 669, 670, 671, 672, 673, 674, 675 Ash, 135, 341 one-bladed, 666, 667 weeping, 196, 596 Ashe, 343 Aster, 132, 152, 242 seashore, 200, 282 Aster Tripolium, 132, 200, 236, 282, 410 Astragalus alpinus, 696 Atavism, 154, 170, 172, 175, 176, 178, 182, 185, 187, 188, 198, 220, 222, 226, 235, 344, 354, 399, 405, 411, 660, 661 bud, 183, 226 definition of, 170, 631 false, 185, 187 negative, 344 positive, 344 seed, 176 systematic, 174, 222, 630-657 Atavists, 156, 201 heredity of, 412 Atropa Belladonna lutea, 592 Aubretia, 241 Avena fatua, 100, 207 Azalea, 178, 322 Azolla caroliniana_, 239

Babington, Manual of British Botany, 36, Bailey, 78, 306, 684 Balsams, 334 Bananas, 90, 134 Banyan, 244 Barberry, 133, 180 European, 270 purple, 596 Barbarea vulgaris, 427 Barley, 98, 105, 133, 203, 678, 679 "Nepaul," 203, 676, 677, 679, 681, 682 Bastard-acacia, 133, 136, 140 Bateson, 250 Bauhin, Caspar, 72, 610 Baumann, 618 Beans, 90, 152, 327, 727, 735 Bedstraw, 648 Beech, 133, 135, 242 cut-leaved, 179, 196, 616 laciniated, 196 oak-leaved, 595 purple, 196, 593, 595 Beeches, 427 fern-leaved, 147 Beets, 68, 72, 92, 93, 792, 796, 801, 815, 817, 818 Californian, 796 European, 796 forage, 71, 72, 791 salad, 71 Beet-sugar, 67, 68, 69, 70, 71, 109, 165, 717, 791, 807, 813, 814 Begonia, 218, 366, 509, 765 ever-flowering, 148 tuberous, 272 clarkii, 272 davisii, 272 rosiflora, 272 sedeni, 273 semperflorens, 133, 148, 620 Begonia bulbous, 372 veitchi, 272 Behrens, 804 Belladonna, 145 Bellis perennis, 236 perennis plena, 195 Bentham, 237 Bentham & Hooker, Handbook of British Flora, 36 Berberis, 133, 180, 455 ilicifolia, 270 vulgaris, 270 Bertin, 596 Berula angustifolia, 457 Bessey, 660 Beta maritima, 69 patula, 69, 70 vulgaris, 69, 70 Betula, 132 Between-race, 358 Bewirkung, Theorie der directen (Nageli), 448 Biastrepsis, 402 Bidens, 131 atropurpurea, 131 cernua, 131, 158 leucantha, 131 tripartite, 131 Bilberries, 577 Bindweed, 41924 Binomium, of Newton, 767 Birch, 133, 243 cut-leaved, 596, 616 fastigiate, 618 fern-leaved, 179 Bisoutella, 282 laevigata glabra, 125 Bitter-sweet, 125 Blackberry, 268, 768 "Paradox," 769 Blue-bells, variation in, 54, 491, 577 Blueberries, 769 Blue-bottle, 499, 507, 509, 510 Blueflag, atavism of, 172 Boehmeria, 675 bilboa, 685 Bonnier, 439, 441, 442, 444, 451, 795 Boreau, 663 Brambles, 126, 127, 147, 239, 244, 245, 268, 740, 769, 663 Brassica, 244 Braun, 738 Braun and Schimper, 494 Bread-fruits, 90 Briot, 618 Britton and Brown's Flora, 162 Brooks, 711 Broom, 140 prickly, 217 Broom-rape, 220 Broussonetia papyifera dissecta, 616 Brunella, 146, 268 vulgaris, 577 vulgaris alba, 201 Bryophyllum calycinum, 218 Buckwheat, 452 Bud-variation, 750 Buds, adventitious, 218 Burbank, Luther, 57, 79, 116, 134, 268, 758, 768, 769, 784 Buttercup, 331, 357, 410, 725, 740 Asiatic, 241

Cabbages, 428, 684 atavism in, 638 origin of varieties, 621 Cactuses, 444 Cactus-dahlia, 625 Calamintha Acinos, 437, 452 Calamus root, 222 Calendula officinalis, 502 Calliopsis tinctoria, 195 Calluna, 146 vulgaris, 437, 577 Caltha, 490 palustris, 331 Camelina, 684 Camellia, 178, 323 japonica, 368 Camellias, 331 Camomile, 130, 132, 156, 366, 494, 503, 509, 512 Campanula persicifolia, 151, 234 rotundifolia, 437 Campion, 283, 302, 304 evening, 281 red, 238 Canna, 751, 759, 761 indica, 760 "Madame Crozy," 760, 761 nepalensis, 760 warczewiczii, 760 Capsella Bursa-pastoris apetala, 585 heegeri, 22, 582, 583, 684 Carex, 53 Carnation, 178, 241, 491 wheat-ear, 227 Carpinus Betulus heterophylla, 180 Carriere, 491, 596, 612, 806 Carrots, 806 Catch-fly, 419 Carboniferous period, 699 Casuarina quadrivalvis, 649 Cauliflowers, origin of, 621 Caumzet, 614 Causation, theory of direct, (Nageli), 448 Cedar, pyramidal, 618 Celandine, 147, 245, 280, 365 oak-leaved, 603, 610, 611 Celosia, 621 Celosia cristata, 327, 411 Centaurea, 242 Centgener power, 20, 822 Centranthus macrosiphon, 424 Cephalotaxus, 170, 226 pedunculata fastigiata, 169 Cereals, 105, 106, 107, 119, 801, 804 origin of cultivation, 104 Character-units, 632 Charlock, 424 Cheiranthus, 490 Cheiri, 370 Cheiri gynantherus, 371 Chelidonium laciniatum, 22, 609 majus, 147, 365, 600, 610, 611 majus foliis quernis, 610 Cherries, 79 Cherry, bird's, 617 Chestnuts, 427 Chromosomes, 306 Chrysanthemum, 178, 274 corn, 739 Chrysanthemum carinatum, 494 coronarium, 161, 202, 510 grandiflorum, 739 imbricatum, 494 indicum, 490 inodorum, 503 inodorum plenissimum, 336 new double, 501 segetum, 202, 493, 504, 729 segetum, var. grandiflorum, 43, 495, 498, 504, 504 Chrysopogon montanus, 450 Cieslar, 804 Cineraria cruenta, 514 Cinquefoil, 52 Clarkia, 420 elegans, 198 pulchella, 282 pulchella carnea, 162 Clematis Vitalba, 662 Viticella nana, 612 Clover, 80, 102, 674 crimson (Italian), 353, 358, 359, 360 five-leaved, 340, 362, 374, 431, 509, 789 four-leaved, 340, 346, 352 red, 235, 281 white, 133, 366 Clusius, 610 Cochlearia anglica, 52 danica, 52 officinalis, 52 Coconut, 67, 82, 83, 87, 88, 89 dispersal of, 85, 89 geographic origin of, 88,89 Coconut-palm, 84, 88 Cockerell, T.D.A., 139, 140, 591 Cocklebur, 139 Cockscomb, 165, 327, 356, 411, 621 Cocos nucifera stupposa, 83, 84 cupuliformis, 82 rutila, 82 Codiaeum appendicularum, 673 Colchicum, 490 Coleus, 132 Columbine, 725 yellow, 161 Columbus, 89, 118 Columella, 106 Composites, 130, 131, 336, 723, 778 Conifers, 168, 226, 239, 455 weeping, 617 Connation, of petals, 660, 661 "Conquests," 242 Contra-selection, 425 Cook, 84, 86, 88, 89 Corn, 81, 90, 118, 119, 135, 283, 287, 288, 775, 786, 788, 804 American, 205 Corn-cockle, 162 Corn-chrysanthemum, 739 Corn-flowers, 491, 92 Corn, "Forty-day," 118 "Harlequin," 327 sterile variety of, 622 sugar, 135, 158 "Tuscarora," 205 Corn-marigold, 493, 494 Cornel berry, yellow, 196 Cornaceae, 675 Cornu, 338 Cornus Mas, 196 Correlation, 142 Corylus, 133 Avellana, 181 tubulosa, 181 Cotton, 725 Cotyledon, 674 variation in, 416 Crambe maritima, 621 Cranesbill, 599 European, 628 meadow, 322 Crataegus, 196 oxyacantha, 132 Crowfoot, 331 corn, 283 Crepis biennis, 410, 411 Cress, Indian, 192 Crosses bisexual, 255, 276, 294, 298 reciprocal, 279 unisexual, 255, 261 varietal (see Hybrids) Croton, 673, 674 Crozy, 760, 762 Crucifers, 222, 635 Cryptomeria, 169, 226 japonica, 239 Cucumbers, 118 Cucumis, 52 Cucurbita, 52 Cultivated plants, 65, 66 elementary species of, 62 improvement of, 92 mixed nature of, 96, 118 origin of, 91 Currants, 79 Californian, 270 flowering, 166 "Gordon's," 270 Missouri, 270 white, 158 white-flowered, 167 Cuttings, 721 Cyclamen, 323, 355, 627, 684 Butterfly, 627 vernum, 619 Cypripedium caudatum, 487 Cytisus adami, 271 candicans Attleyanus, 367 Laburnum, 271 prostratus, 139 prostratus ciliata, 125 purpureus, 271 spinescens, 139

Dahlia, 131, 241, 272, 625 cactus, 625 "Jules Chretien," 628 purple-leaved, 626 "surprise," 230 tubular, 627 274, 490, 764 first double ones, 490 green, 227, 229, 230 Daisies, 131, 132, 494 double, 195 hen-and-chicken, 514 ox-eye, 202 Shasta, 769 yellow, 202 Dandelion, 411 parthenogenesis, 61 variations in, 60 Daphne Mezereum, 146 Darwin, 1, 2, 3, 4, 5, 6, 7, 18, 76, 85, 93, 109, 110, 180, 196, 205, 206, 242, 306, 324, 338, 448, 571, 604, 612, 689, 702, 710, 715, 743, 798, 825 Darwin, George, 711 Darwinian theory, 461 basis of, 5 Date, 134 Datura Stramonium, 139, 142 Stramonium inermis, 300 Tatula, 139, 142, 300 Dead-nettle, 237 De Bary, 38, 47, 49 De Candolle, 76, 84, 85, 89, 228, 370, 403, 621 Alphonse, 74, 129, 226 A.P., 129 Casimir, 659, 676 De Graaff, 275 Delphinium Ajacis, 192 Deniau, 617 Descent, theory of, 690, 694, 702, 707, 716, 798 De Serres, Olivier, 72 Desmodium gyrans, 655, 656, 663, 664, 65 Dewberry, California, 269 Dianthus barbatus, 322, 648 twisted variety, 408 Diatoms, 699 Dictoyledons ancestors of monocotyledons, 15 Digitalis parviflora, 161, 640 purpurea, 483 pelorism of, 482 Dimorphism, 445, 447, 454, 457, 458 Dippe, 810 Dipsacus fullonum, 402 sylvestris, 402, 402 Dominant character, 280 Double flowers poppies 490 production of, 489 types of, 330 Double races (see also ever-sporting varieties), 419, 427, 428 Dubois, Eugene, 712 Duchesne, 185, 188, 596 Duckweed, 222 Draba, 692, 693 verna, 47, 50, 51, 53, 125, 126, 518, 533, 546, 547, 561 Dracocephalum moldavicum, 419 Dragon-head, 419 Drosera anglica, 268 filiformis, 268 intermedia, 268 obovata, 267 rotundifolia_, 268

Earth, age of, 710 Edelweiss, 438 Eichler, 660 Election, 801 Electric light, growth in, 442 Elementary species, 11, 13, 32, 67, 74, 76, 77, 78, 79, 91, 95, 116, 119, 124, 126, 128, 129, 207, 238, 252, 256, 307, 430, 435, 695, 696, 698, 702, 715, 787, 798, 800, 825 apples, 75 coconut, 82 corn, 81 cultivated plants, 62 definition of, 12, 35, 127 flax, 80 how produced, 16, 248 hybrids of, 253, 255 mutation of, 141 origin of, 459, 603 origin of, how studied, 463 selection of, 92 varieties vs., 14, 15, 141, 152, 224, 243, 247, 251, 495 Elm, 136, 219, 239, 427 Epilobium, 268 hirsutum, 683 hirsutum cruciatum, 588 montanum, 269 tetragonum, 269 Equisetum Telmateja, 642, 649 Erica Tetralix, 577, 661 Ericaceae, 146, 660 Erigeron Asteroides, 450 canadensis, 132, 236, 453, 600, 695 Erodium, 146 cicutarium album, 161 Erucastrum, 630, 638, 639 pollichii, 222, 637 Eryngium campestre, 674 maritimum, 674 Erysimum cheiranthoides, 638 Erythraea pulchella, 452 Erythrina, 621 Crista-galli, 620 Eschcholtzias, 59 Esimpler, 337 Eucalyptus citriodora, 669 Globulus, 217 Euphorbia Ipecacuanha_, 55 Evening-primrose, 62, 204, 256, 424, 686, 687, 688, 690, 691, 694, 695, 699, 702, 703, 705, 707, 708, 713, 747, 793 Evolution, 93, 685, 686, 689, 704, 707, 709, 710, 713, 718 degressive, 222, 223, 249 progression in, 630 progressive, 221, 222, 223, 248 regression in, 630 regressive, 221, 222; 223, 24 retrograde, 221, 631 Extremes, asexual multiplication of, 742, 769

Fabre, 265 Fagus, 133 Fagus sylvatica pectinata, 179 Fan, genealogical, 700 Fasciated stems, 409, 412 Ferns, 63 cristate, 427 plumose, 427 Ficaria, 53 Ficus radicans, 436 religiosus, 244 repens, 436 stipulata, 436 ulmifolia, 436 Figs, 436 Filago, 52 Fir, 134, 804 Fittest, survival of, 826 Flax, 80, 805 springing, 80 threshing, 80 white-flowered, 158, 160 Fleabane, Canada, 132, 236 Flowers, gamopetalous, 660 Fluctuability embryonic, see Fluctuation, individual Fluctuation, 708, 715, 716, 718, 719, 724, 737, 741 curves of, 729, 794 defined, 191 individual, 718, 723, 732, 741, 745, 749, 788 mutation vs. 7, 16, 719 partial, 718, 723, 732, 741, 745, 748, 749, 771 inadequate for evolution, in elementary species, 19 nature of, 18 specific and varietal characters vs. 17 Forget-me-not, 368 Fothergill, John, 521 Foxglove, 163 peloric, 164, 356, 367 yellow, 161, 640 Fraxinus excelsior monophylla, 667 exheterophylla, 667 simplici folio, 667 French flora (Grenier and Godron), 433 Fries on Hieracium, 60 Frostweed, 440 species of, 52 Fuchsia, 272, 355 Fuchsias, 491

Gaertner, 279 Galeopsis Ladanum canescens, 139 Galium, 648 Aparine, 409, 648 elatum, 52 erectum, 52 Mollugo, 62 verum, 648 Gallesio, 138 Galton, 736, 776 Gamopetaly, 662 Garden-pansy, origin of, 38 Garlic, 638 Gauchery, 452 Geikie, 711 Genera artificial character of, 36 polymorphous, 692 Gentiana punctata concolor, 125 Gentians, 577 Georgics (Vergil), 106 Geranium pratense, 323, 628 album, 628 pyreniacum, 599 German flora (Koth), 432 Geum, 282 Gherkins, 118 Gideon, Peter M., 78 Glacial period, 696 Gladiolus, 241, 272, 274, 368, 765 cardinalis, 275 gandavensis, 275 psittacinus, 275 purpureo-auratus, 275 Glaucium, 241 Gleditschia sinensis, 614 triacanthos pendula, 617 Gloxinia, 282, 485 erect, 626 Gloxinia erecta, 485 peloric variety, 485 Gnaphalium Leontopodium, 438 Godetia amoena, 161 Godetias, 59, 232 Godron, 265, 432 Goeppert, 370 Gooseberry, 79, 140, 626 red, 133, 165, 241 Grapes, 90, 158, 328 Grape-hyacinth, plumosa, 134 Grasses, 102, 631, 681 Grenier, 433 Groundsel, 132 Growth, nutrition and, 714, 720, 722 Guelder-rose, 134, 239 Gum-tree, Australian, 217 Gypsophila paniculata twisted variety, 409

Haeckel, 707 Half-races, 358, 372, 409, 419, 424, 427, 428 Hall, 444 Hallet, F.F., 109 Harebell, 232 peach-leaved, 234 Harris, Arthur, 825 Harshberger, John W., 591 on Euphorbia in New Jersey, 55 Hawksbeard, 410, 411, 412 Hawkweed, 411, 439, 443, 819 Hawkweeds seeding without fertilization, 61 Hawthorn, white, 132 Hays, W.M. on individual selection, 20, 94, 95, 117, 821, 823, 824 Hazelnut, 133, 181, 242 Hazels, cut-leaved, 596,-616 Heath family, 146, 222, 660 Heaths, origin of, 662 Heather, 577 Hedera Helix arborea, 437 Hedgehog burweed, 140 HedysArum, 664 Heeger, 582 Heer, Oswald, 74, 105 Heinricher, 172, 173, 174 Helianthemum, 53, 125, 126, 561 apenninum, 52 pilosum, 52 polifolium, 52 pulverulentum, 52 vulgare, 440 Helichrysum, 420 Helwingia, 678, 678, 682 rusciflora, 675 Hemp, 419 Henbane, 282 Hepatica, 322, 490 Heredity, 731, 734, 818 bearers of, 632 in teasels, 642 Hesperis, 241, 322 matronalis, 323, 411 Heylandia latebrosa, 450 Hibiscus Moscheutos, 591 Hieracium, 59, 439 alpinum, 696 Hildebrand, 160, 240, 241 Hoffman, 160, 662 Hofmeister, 160, 370, 480 Holbein, 164, 596 Holly, 140, 196 Holtermann, 449, 451 Hollyhock, 427 Honeysuckle, 674 ground, 443 Hordeum distichum, 677 hexastichum, 677, 678 tetrastichum, 677 trifurcatum, 676, 678 vulgare trifurcatum, 203 Hornbeam, European, 180 Horse-chestnut, 219 thornless, 234 Horsetail, Canadian, 695 European, 649 Horsetail, family, 641 Horse-weed, 132 Canadian, 452 Hortensia, 134, 181 Horticulture, mutations in, 604 Houseleek, 370, 371 Hunneman, John, 521 Hyacinths, 178, 322 white, 160 Hybrids, 58, 201, 202, 206, 250, 575 between elementary species, 253 constant, 263, 264, 265, 266, 267, 268, 269 law of varietal, 716 Mendelian, 324 nature of, 20 species, 256, 260 splitting of, 210 varietal, 208, 209, 247, 277, 278, 279, 281, 285, 293, 294 Hybridization, 706, 751, 752, 758, 759, 764 Hydrocotyle, 668 Hyoscyamus niger, 282 pallidus, 283 Hypericum perforatum, 725 Hyssopus officinalis_, 161

Iberis umbellata rosea, 195 Improved races, inconstancy of 770-797 Indian cress, 668 pelorism of, 485 Indian pipe, 661 Ipecac spurge, 55 Iris, 456 falcifolis, 172 kaempferi, 174 lortetii, 521 pallida, 172 pallida abavia, 681 Isolation, 108 Ivy, 436

Jacob's ladder, 200, 202 Jacques, 614 Jacquin, 52, 632 Jaggi, 594, 595 Jaeger, 228, 662 Jalappa, 165 Janczewski, 266 Japanese plum, 58 Jasminum Sambac, 662 Joly, 712 Jordan, Alexis, 45, 47, 49, 50, 129 experiments with species, 37, 40 Juncus effusus spiralis, 684 Juniper, 684

Kapteyn, 716 Kelvin, Lord, 720, 711 Kerner von Marilaun, 266, 267 Keteleer, 618 Knight, 390, 719, 720 Koch, 433, 667 Koelreuter, 279 Korshinsky, 609, 612, 614, 617, 667 Krelage, 510, 619 Kuhn & Co., Messrs., 801, 809, 817

Labiates, 237 pelories of, 577 Labiatiflorae, pelorism of, 468 Labrador tea, 661 Laburnum, 270, 284, 342 oak-leaved 147, 179 pelorism of, 485 Lactuca, 52 Scariola, 456 Lagasca, Mariano, 96, 97, 114 Lamarck, 1, 447, 461, 522, 522 Lamarckism objections to, 449 Lamium album, 237 maculatum, 237 pelorism of, 486 purpureum, 237 Larch, 804 Larkspur, 124, 192, 311, 452 hybrid, 213 white, 160 Latency, 657 individual, 219 specific, 246 systematic, 219, 220, 235 varietal, 246 Latent characters, 216 Lathyrus odoratus, 776 Laurea pinnatifida, 450 Laurel, lady's, 146 Laurent, 802 Leaves, cleft, 685 variegated, 426, 431 LeBrun, Mme., 614 Le Couteur, 96, 97, 107, 108, 114, 115, 116, 742 Ledum, 222, 661 Lemna, 222 Lemoine, 762, 762 Lettuce, 684 crisped, 158 prickly, 456 Life, struggle for, 103, 119, 120 Lilacs, 59, 769 double, 762 Lilium candidum flore pleno, 331 pardalium, 116 Lime-tree, 355, 366, 428, 669 fern-leaved, 147 Linaria, 467, 471, 480 dalmatica, 482 genistifolia, 267 italica, 267 vulgaris, 267, 471 vulgaris peloria, 464 Lindley, 63, 129, 506 Linnaeus, 32, 33, 129, 132, 256, 663 on the idea of species, 11, 13 on origin of species, 2, 34 on primroses, 52 Linum angustifolium, 80 crepitans, 81 usitatissimum, 80, 161 Link, 466 Liver-leaf, 322 Lobelia syphilitica, 161 Lonicera etrusca, 640 tartarica nana, 614 Lorenz, Chr., 482 Lothelier, 454 Lotus corniculatus, 442 corniculatus hirsutus, 139 London, 615, 616, 667 Lucerne, 264 Ludwig, 738 Lupines, 90 Lychnis, 282 chalcedonica, 161 diurna, 238, 578 preslii, 578 vespertina, 238, 281, 585 Lycium, 455 Lycopersicum, 655 grandifolium, 654 latifolium (see L. grandifolium). solanopsis, 854, 656 validum (see L. solanopsis). Lyell, 1, 710 Lysimachia vulgaris, 684

MacDougal, D.T., 62, 575, 590 Macfarlane, 56, 255, 268 Madia elegans, 779 Magnolia, 355, 366, 428, 674, 675 obovata, 355, 669 Magnus, 228 Mahonia aquifolia, 270 Maize, 134, 775 "Cuzco," 152 European, 206 "Gracillima," 152 "Horse-dent," 152 "Quarantino," 118 Mallow, 663, 684 Malva crispa, 684 Maples, laciniate, 615 Marchant, 592 Marigold, 131, 158 corn, 729 field, 503, 505, 508 garden, 503 Japanese, 490, 494, 495 Marsh-marigold, 331 Martinet, 80 Measart, 434 Masters, 228, 370, 372 Matricaria Chamomilla, 130 Chamomilla discoidea, 156 Matricaria discoidea, D.C., 157 May-thorn, red, 196 Medicago media, 264 falcata, 264 Melanium, 39 Melons, 118 Mendel, 6, 210, 294, 296, 306, 308 Mendel's law, 276, 293, 294, 298, 299, 300, 301, 307, 612, 613, 616, 716 Mendelism, 307 Mentha, 52 Mercurialis annua, 420 annua laciniata, 592 Mercury, 420, 422, 425, 820 Methods of investigation, 21 Metzger, 205, 206 Milde, 38 Milfoil, 441 Millardet, 266 Miller, 611 Millet, 105 Mimulus, 151 quinquevulnerus, 725 Mimusops, 697 Miocene period, 698 Miquel, 83 Mirabilis, 241 Jalappa, 322 Mirbel, 615 Monardella macrantha, 444 Monstrosities, 400, 401, 445, 446, 447 Monkey-flower, 725 Monocotyledons ancestry of, 1, 5 regression in, 630 Monotropa, 222, 661 Morphologic units, 145, 152 Monstrosities, 818 Morgan on mutation-theory, 9 Morren, 244, 762 Mountain-ash, 342 Muller, Fritz, 775, 776, 780 Multiplication, vegetative (see Asexual propagation) Munting, Abraham, 164, 165, 490, 762 Munting's drawings, 512 Murr, 158, 236 Muscari comosam, 134 Museum d'Histoire Naturelle, Paris, 522 Mutability vs. fluctuating variability, 568 Mutation, 659, 674, 677, 685, 686, 694, 713, 716, 825 absence of intermediate steps in, 474, 480 conditions for observing, 601 decided within the seed, 28 definition of, 7 easily observed, 30 experimental, 688 few observations of, 8 fluctuation vs., 7, 16, 719 influence of on variability, 335 iterative nature of, 476, , 703 laws of, 556, 558, 560, 562, 564, 566, 568, 570 limited in time, 29 observation of, 16 in Oenothera, 521, 525, 690 oldest known, 609 oldest recorded, 22 periodic, 690, 692, 694 perodicity of, 519 progressive, 307 repetition of, 476 in Saponaria calabrica, 612 simultaneous, 614 in tomato, 655 Mutations, 141, 275, 280, 445, 449, 573, 608, 620, 626, 678, 685, 686, 701, 704, 712, 713, 716, 800 artificial, 402 chance for useful, 598 defined, 191 frequency of, 597 in garden-flowers, 488 in horticulture, 604, 706 latent, 703 mode of appearance, 517 numerical proportion of, 475 original production of, 702 peloric, 707 periodic, 686, 705 progressive, 704 retrograde, 704 stray, 704, 705, 706 synonyms of, 191 Mutation-period, 714 Myosotis azorica, 368 Myrtus communis, 684

Nageli, 60, 439, 443, 448, 795 Nagelian principle, 448, 450, 451 Natural selection, 18, 119, 120, 445, 456, 682, 694, 703, 743, 744, 798-826 basis, 604 nature of, 6, 19 Naudin, 118 Nectarines, 137, 138, 226, 627 Nemec, 578 Neo-Lamarckians principle of, 8 Neo-Lamarckism 447 Nepenthes, 671, 672, 673, 674 Newton, 1, 732, 767 Nicandra, 152 Nigella, 134 Nightshade, 298 black, 282 Nourishment meaning of, 732 variability and 771 Nuphar, 268 Nutrition and growth, 720, 722 Nymphaea, 698

Oats, 98, 100, 101, 105, 112, 113, 115, 119, 133, 452 "Early Angus," 115 "Early Fellow," 115 "Fine Fellow," 115 "Hopetown," 112 "Longfellow," 115 "Make-him-rich," 112 wild, 207, 803 Oak, 136, 239 Oenothera, 260, 262, 279, 700, 706, 708, 709 European species, source of, 575 mutation in, 521, 525, 585, 690, 708 new species of, 516-546 albida, 537, 553, 555, 563, 565, 573 biennia, 82, 205, 256, 257, 258; 259, 262, 263, 264, 521, 524, 527, 574, 575, 586, 587, 683, 690, 708 biennis cruciata, 22, 587 brevistylis, 263, 280, 526, 529, 530, 547, 563, 564, 565, 573, 574, 702, 706 cruciata, 575, 585, 586, 589, 590, 683 elliptica, 540, 545, 555, 562 gigas, 533, 534, 535, 536; 537, 553, 554, 563, 565, 566, 567, 573, 574, 702 glauca, 424 hirtella, 262 laevifolia, 526, 528, 529, 547, 563, 564, 573, 574, 701, 706 lamarckiana, 17, 262, 262, 522, 523, 527, 528, 529,, 533, 574, 575, 586, 690, 699 pollination of, 524 lata, 540, 541, 542, 549, 550, 551, 552, 555, 559, 563, 566, 573, 574, 702 leptocarpa, 540 muricata, 256, 257, 258, 259, 262, 263, 264, 513, 575, 690 pollination of, 524 nanella, 526, 531, 549, 50, 551, 552, 555, 563, 564, 565, 566, 703 oblonga, 537, 538, 552, 555, 563, 565, 566, 572 rubrinervis, 533, 534, 536, 537, 550, 551, 552, 555, 563, 565, 568, 573, 574 scintillans, 540, 543, 553, 555, 563, 566, 573, 574 mutability of, 544 semilata, 540 suaveolens, 521 Oleander, 684 Onagra, 262, 708, 709 Onions, wild, 684 Ononis repens, 577 Orange, 90, 133, 134 Orchids, 631 Origin of species (Darwin), 109 Orobanche, 220 Othonna crassifolia, 442 Otin, 618 Oviedo, 89

Paeonia corallina leiocarpa, 126 Paillat, 618 Pangenes, 306 Pangenesis, 306, 689 Panicum, 105 Pansies, 640 Pansy, 118, 121 Papaver alpinum, 139 bracteatum, 661 bracteatum monopetalum, 661 commutatum, 357 dubium glabrum, 126 hybridism, 662 somniferum Danebrog, 162 somniferum monstruosum, 371 somniferum polycephalum, Parris, 754 Parsley crisped, 158, 181 Parsnip, water, 457 Pea-family, 344 Peach, 138, 226, 240 Peach-almond, 769 Pears, 79, 90, 134, 147, 152, 203, 283 Pearson, Karl, 716 Peas, sugar, 135, 158 Pedicularis, 410 palustris, 410 Pedigree-culture, 109 experimental, 547 Pelargonium, 272, 355 Peloria, definition of, 164 Peloric toad-flax first record of, 466 origin of, 459, 464, 472 sterility of, 467 Pelorism Antirrhinum majus (see snapdragon) Digitalis purpurea, 482 Gloxinia, 484, 485 labiates, 486 Laburnum, 485 Lamium, 486. Linaria, see Toad-flax Linaria dalmatica, 482 Linaria vulgaris, 464 orchids, 479, 486, 487 Salvia, 486 Scrophularia nodosa, 486 snapdragon, 481 toad-flax, 459-487 Tropaeolum majus, 485 Uropedium Lindenii, 487 wild sage, 486 Peltaria alliacea, 663 Pennywort, marsh, 668 Penzig, 638 Periodicity, law of, 365, 368, 721, 722 Periods, mutative, 706, 708 Periwinkles, 322 Persicaria, water, 433, 434, 435, 643 Petalomany, 330 Petunia, 491, 626 Phacelia, 420, 422, 820 Phaseolus lunatus, 592 multiflorus, 202 nanus, 202 Phleum alpinum, 696 Phlox, 232 drummondi, 161 Phyllonoma ruscifolia, 676 Physiologic units, 144, 153, 249 Picris hieraoioides, 411 Pimpernel, scarlet, 162 Pinacothec, Munich, 164 Pine, 368, 804 Pine-apples, 90, 134 Pinks, 178 Pinus sylvestris, 368 Pistillody in poppies, 369, 370, 372 Pitcher-plants, 671 Plankton, 711 Plantago, 53 lanceolata, 520, 671, 684 Plantain, 684 Plater, 610 Plum, 79, 134, 789 beach, 58 Japanese, 58 purple-leaved, 619 Plusia, 204 Poa alpina vivipara, 684 Podocarpus koraiana, 169 Polemonium coeruleum, 282 coeruleum album, 200 dissectum, 161, 202 Polygala, 242 Polygonum amphibium, 432 var. natans Moench, 433, 434 var. terrestris Wench, 433, 434 Convolvulus, 419, 424 viviparum, 684 Polymorphy, 188 Pomegranate, 90 Pond-lily, yellow, 268 Poplar, fastigiate, 623, 624 Italian, 623 Populus italica, 622 nigra, 624 Poppy, 146, 151, 152, 163, 165, 241, 356, 640, 723 "Danebrog," 283, 291 garden, 661 "Mephisto," 283, 291 opium, 89, 189, 195, 198, 282, 291, 369, 371, 373, 379, 383, 391, 405, 406, 420, 452, 720, 789 pistillody in, 369 pistilloid, 508 polycephalous, 405 Potatoes, 765, 810 Potentilla Tormentilla, 52 Pre-Linnean attitude, 2 Primrose, 268, 372, 410 evening (see evening-primrose). Primula acaulis, 52, 632 elatior, 52, 633, 635 grandiflora, 268 imperialis, 697 japonica, 410 officinalis, 52, 268, 633, 635 variabilis, 268 veris, 52, 633, 634 Prodromus (De Candolle) 370 Progression, 430, 705, 774, 775, 777, 779, 805 in evolution, 630 Propagation asexual, 745, 751, 766, 767, 770, 774, 777 sexual, 745, 777 vegetative (see asexual) Proskowetz, Em. von, 70 Prototype definition of, 170 Prunus, 52 cerasifera, 619 Mahaleb, 617 nana, 612 maritima, 59 Padus, 617 Pissardi, 619 variation in, 56 Pyrethrum roseum, 511 Pyrola, 222, 661

Quartile, 736, 737, 767 Quercus pedunculata fastigata, 596 Quetelet's law, 463, 716, 717, 725, 730, 734, 738, 748, 753, 759, 767, 775, 779, 780, 806

Races, inconstancy of improved, 770-797 Raciborsky, 682 Radishes, 325, 806 Ragwort, tansy, 157 Raisins, 134 Rameses, 697 Ranunculus, 331 acris, 331 arvensis, 282 arvensis inermis, 125 asiaticus, ,241 bulbosus, 357, 410, 740 Ra-n-Woser, King, 104 Raphanus Raphanistrum, 202, 424,520 caudatus, 202 Rasor, John, 588, 589 Raspberry, 268, 768 "Phenomenal," 268 "Primus," 269 Siberian, 269 Ratzeburg, 467 Raunkiaer on variation in Taraxacum, 60 Recessive character, 280 Sports, 191, 715, 689 bud, 427

Sprenger, 610, 611 Stability, 155 Stahl, 611 Stellaria Holostea apetala, 585 Stocks, 146, 322, 328, 329, 332, 334, 336, 338, 432 Stock "Brompton," 329 chamois-colored, 198 "Queen," 324 white, 160 Stork's-bill, white hemlock, 161 Strasburger, 196, 448 Strawberry, 158, 266, 342 "Gaillon," 135 "Giant of Zuidwijk," 614 one-leaved, 164, 596, 666 white, 158, 165 Striped flowers, 309, 374, 431, 606, 607 races, types of, 328 Struggle for life, 674, 571, 682, 702, 799, 803, 824, 825 St. Johnswort, 725 St. Sebastian, 164 Sub-species (see also Elementary species), 224, 225 Sugar-beets (see Beets, sugar) Sugar-cane, 731, 752 "Black Manilla," 753 "Cheribon," 753, 755, 756 "Chunnic," 753 "Hawaii," 755, 756 seeds of, 754 "White Manilla," 752 Sundew, 268 Sunflower, 410, 425, 820 Sweet-flag, 222 Sweet-pea, 160, 776 Sweet William, 163, 282, 322, 648 twisted variety, 408, 648 Syncotyls, 417, 424 Syringa vulgaris axurea plena, 763 Systematic species, 12, 64, 101, 128 nature of, 54, 62 Systematic units, 61, 91

Tagetes africana, 510 signata, 612 "Talavera de Bellevue," 97 Tanacetum vulgare, 131, 132, 236 Tansy, 131, 132, 236 Taraxacum, 125, 126 officinale, 59, 411 Tares, 105 Taxus, 136 baccata, 169 baccata fastigiata, 170, 618 minor, 169 Teasels, 402, 642, 645, 674, 675 twisted, 405, 412, 446, 447, 643, 646, 647, 648, 819 Tetragonia expansa, 162 Theatre d'Agriculture, 72 Thibault, 618 Thomson, Sir William (see Kelvin, Lord) Thorn-apples, 139, 142, 143, 145, 238, 283, 300, 452 thornless, 234 Thorn-broom, 457 Thrincia hirta, 411 Thuret, 38, 47, 49 Thyme, white creeping, 201 Thymus Serphyllum album, 201 vulgaris, 577 Tilia parvifolia, 355, 669 Toad-flax, 267, 282, 707 cross pollination of, 471 experiment with, described, 468 invisible dimorphous state of, 470, 471, 478 latent tendency to mutation in, 479 peloric, see Peloric toad flax sterility of mutants, 477 unusual pelorism, 486 Tomato, 653 "Acme," 656, 657 "Mikado," 654 mutation of, 655 upright, 654 "Washington," 657 Tournefort author of genera, 32 Tracy, W.W. 592 Trees, genealogic, 707, 708 Tricotyls, 416, 419, 420 Trifolium incarnatum, 352 Triticum dicoccum, 105 Tropaeolum, 193, 668 majus, pelorism of, 485 "True Exercises with Plants" (hunting), 490 Tulips, 149, 178, 274, 322 black, 620 Turnip, 244, 621 Twisted stems, 402, 403, 405, 413 Twisted varieties atavists of, 406

Ulex europaeus, 140, 217 Ulmus pedunculata, 615 pedunculata urticaefolia, 615 Umbellifers, 457 Umbilicus, 669 Unger, 105 Unit-characters, 249, 261, 306, 307, 313, 658, 689, 715, 716 Urban, 265 Uropedium lindenii, 487 Utility, 685, 724 Utricularia, 672

Vaccinium Myrtillus, 577 Valerian, 402, 409, 648 twisted, 403 Valeriana officinalis, 402 Vallisneria, 684. Van den Berg, 625 Van de Water, 614 Van Mons, 76, 77, 78, 806 Variability (see also Fluctuation ), 188, 190, 191 analogous, 244 apple, 75 asexual, 320 correlative, 142, 143, 148, 167 cultivated plants, 66 embryonic, 770, 771, 814 ever-recurring, 190 fluctuating (see also individual), 62, 142, 190, 233, 375, 416, 454, 698, 759, 762, 765, 766, 767, 770, 771, 789, 805, 814 fluctuating vs. mutability 569 homologous, 244 individual (see also fluctuating), 190, 716, 718, 746, 749, 770, 814 influence of mutation on, 335 kinds of, 715 nutrition and, 390, 391, 719, 771 parallel, 243 partial, 440, 444, 718, 746, 748, 753, 814, 816 repeated, 242 restricted, 598 sectional, 317 sexual, 320 sources of, 758 Variation bud, 176, 178, 180, 284, 317, 318, 321, 338, 427, 750 definition of, 188 partial, 788, 789 seed, 750 spontaneous, 191 use of term, 189 Variegation, 426, 427 Varietal marks, origin of, 275 Varieties, 84, 95, 126, 127, 128, 129, 132, 142 broom-like, 618, 624 constancy of, 532 constant, 135 crosses of species with, 247, 277, 278, 281 elementary species vs. 459 ever-sporting, 178, 309, 310, 311, 312, 313, 321, 324, 328, 329, 332, 333, 334, 350, 358, 365, 368, 372, 399, 413, 420, 430, 431, 432, 434, 445, 606, 607, 628, 740, 789, 790, 795 fasciated (see Fasciated stems). groups of, 606 horticultural, 607, 609 hybrid, 122, 190, 608 hybrids of, 210, 254, 255 inconstant, 135, 154; 155, 161 mutation of, 141 negative (retrogressive), 131, 132, 134, 224, 226, 238, 245, 277 positive, 131, 132, 134, 224, 238, 245 pure, 122, 190 retrograde, 14, 15, 16, 95, 121, 208, 430, 435, 606, 607 retrogressive (see negative). seed, 122 single, 191 spontaneous crosses, 209 sporting (see inconstant) stability of, 207 sterile, 622 types of, 142 variable, 606 vegetative, 122 weeping, 617 Variety, 130 definition of, 11, 12 elementary species vs. 141, 152, 154, 224, 243, 247, 251 origin of, 141, 152, 224 use of term, 189, 435 Variety-testing, 95, 97, 116, 119, 743, 799, 825 Varro, 106 Veitch & Sons, 272 Venus' looking-glass, 367 Verlot, 186, 612 Vernon, 132 Vernonia cinerea, 450 Veronica longifolia, 282, 284 scutellata, 139 spicata nitens, 126 Viburnum Opulus, 134, 239 Vicinism, 185, 188, 203, 205, 206, 213, 214, 776 definition of, 188, 192, 606 Vicinist, 199, 201 Vicoa aurioulata, 450 Victoria regia, 668 Villars on Draba verna, 49 Vilmorin, 570, 607, 612, 622, 661, 662, 773, 775, 776; 792, 795, 796, 797, 806, 807, 810, 813, 818, 820 Vilmorin, Louis de, 72, 92, 93, 97, 108, 109, 110, 114, 185, 818 Vilmorin, Messrs., 322 Vinca, 242, 490 minor, 322 Vine, parsley-leaved, 179 Viola, 126, 546, 547, 692 agrestis, 45 alpestris, 40 altaica, 39 anopetala, 44 arvensis, 39, 40, 41, 44 curtisepala, 45 striolata, 45 aurobadia, 44 caloarata, 39 cornuta, 39, 281 lutea, 38 lutescens, 44 nemausensis, 45 ornatissima, 44 palescens, 45 patens, 45 roseola, 44 segetatis, 45 stenochila, 41 tricolor, 38, 40, 41, 44, 46 ammotropha, 41 coniophila, 41 genuina, 42 versicolor, 42 Violets, 63, 232, 233, 490 Violet, dame's, 322, 323, 411 long-spurred, 281 Virgil, 105, 106, 108 Viscaria oculata, 4, 648, 821 twisted variety, 408 Vitis, 52 Volckamer, 228 Von Lochow, 821, 822, 822 Von Rumker, 94 Von Wettstein, 448, 805 Vrolik, 164, 483

"Waare Oeffeninge der Planten" (Munting), 490 Wallace, 5, 7, 8, 30, 205 Wall-flower, 370, 371 Walnut, 243, 766 cut-leaved, 616 one-bladed, 666 Water-lilies, 668 Weber, 228 Weeping-willow, 180 crisped, 181 Weigelias, 740 Wellingtonia, 618 Wheat, 96, 98, 105, 113, 119, 283, 810, 823 bearded, 98 "Blue-stem," 117 "Galland," 100, 207 "Hopetown," 112, 112 "Hunter's," 111, 112 "Minnesota No. 169," 117 "Mungoswell's," 110, 111 "Pedigree," 109 "Pringle's," 114 "Rivett's bearded," 207 "Sheriff's bearded red," 114 "Sheriff's bearded white," 114 "White Hunter's," 112 Wheat-ear carnation, 227 White, C.A., 656, 657 White varieties, 577 Whitlow-grasses, 63, 118, 119 Whorls, ternate, 684 Wild sage (see Salvia) Willdenow, 468, 666, 667 Williamson, 491 Willows, 135, 267 Willow weeping (see Weeping-Willow) Willow-herb, 268, 269, 682 Wintercress, 427 Wintergreen, 661 Wittmack, 682 Wittrock, 38, 40, 41, 42, 43, 44, 45, 46 Wooton, E.O., 140 Wormseed, 638

Xanthium canadense, 140 commune, 140, 152, 591 commune Wootoni, 22 Wootoni, 140, 152, 591

Yarrow, 131, 132 Yew, 136, 169 pyramidal, 618

Zea Mays cryptosperma, 641 tunicata, 641 Zinnia, 490 Zioberg, 466 Zocher & Co., 230