Part 81

=B.= HELIANTHEÆ. Most frequently a bract to each flower is found on the receptacle. The pappus is never exactly hairy, but consists of scales, spines, etc., and the fruits are most frequently compressed (Fig. 606 c).--Helianthus (Sun-flower); H. tuberosus (Jerusalem Artichoke) has tuberous underground stems. Dahlia has tuberous roots (Am.). Bidens (Bur-marigold, Fig. 606 c); the fruits are compressed with 2 (or more) spines provided with reflexed barbs.--Calliopsis; Rudbeckia; Zinnia; Tagetes has united involucral leaves, and yellow, transparent oil-glands. Spilanthes, Galinsoga, Melampodium, Silphium (Compass-plant), Helenium, Gaillardia.

=C.= CALENDULEÆ have 1–2 rows of involucral leaves, a naked receptacle, and large, crescent-shaped, irregularly warted fruits, of different forms in the same capitulum; pappus absent (Fig. 605).--Calendula (Marigold); ray-flowers ♀, disc-flowers ♂.

=D.= SENECIONEÆ, have a fine, hairy, white pappus; no bracts, otherwise as in Anthemideæ. The involucral leaves are most frequently in 1–2 rows.--Senecio (Groundsel) has two whorls of involucral leaves, which most frequently have black tips, the external being much shorter than the internal ones (S. vulgaris has all flowers ☿ and alike).--Cacalia, Doronicum, Cineraria, Ligularia, Arnica (A. montana; large, long-stalked capitula; leaves opposite, forming a kind of rosette).

=E.= ASTEREÆ have a bristle-like, unbranched pappus, often of a dingy brown; receptacle naked; involucral leaves numerous, imbricate.--Solidago (Golden-rod); capitula small, yellow-flowered, borne in panicles. Aster; disc-flowers most frequently yellow, ray-flowers violet; Callistephus; Erigeron (Flea-bane)--Inula.--All the corollas are tubular in: Gnaphalium (Cud-weed); involucral leaves dry, rattling, often coloured; the foliage-leaves and stem often white with woolly hairs; ray-flowers ♀, with narrow, tubular corolla; disc-flowers ☿ (few). Antennaria (Cat’s-foot; diœcious), Filago, Helichrysum, Ammobium, Rhodanthe and others. Leontopodium (L. alpinum, “Edelweiss”).

=F.= AMBROSIEÆ, a very reduced type of Compositæ, differing from the others in having free anthers; the capitula are generally unisexual, monœcious, the ♂ borne in a terminal inflorescence, the ♀ in the leaf-axils. In other respects they are most closely related to Heliantheæ.--Xanthium. In the ♂-capitula there are many flowers without calyx, but with tubular corolla and free involucral leaves. In the ♀-capitula there are only 2 flowers, which are entirely destitute of both calyx and corolla; involucral leaves 2-spined, united to form an ovoid, bilocular envelope, each compartment containing one flower. The envelope of involucral leaves unites with the fruits, enclosing them at maturity with a hard covering from which numerous hook-like spines project, assisting very greatly in the distribution of the fruit. The whole structure thus finally becomes a 1- or 2-seeded false nut.--Ambrosia, the ♀ capitulum 1-flowered.

POLLINATION. The flowers are somewhat insignificant, but become very conspicuous owing to a number being crowded together in one inflorescence. The corollas of the ray-flowers, being often very large (Astereæ; Centaurea), frequently render the capitula still more conspicuous. The capitula display many biological phenomena similar to those often shown by the individual flowers in other orders, e.g. by periodically opening and closing, in which the involucral leaves resemble the calyx in their action. (The name “Compositæ” originates from the term “flos compositus,” composite flower). An abundance of honey is formed, which to some extent fills up the corolla-tube, and since insects may visit a number of flowers in the course of a short period they are very frequently visited, especially by butterflies and bees. The pollination has been described on page 567. Protandry is universal. In the bud the tips of the styles, covered by the sweeping-hairs, lie closely enveloped by the anther-tube; in the next stage the style grows through the tube and sweeps out the pollen as it proceeds; ultimately the stylar branches expand and the stigma is then prepared to receive the pollen. In many, the sensitiveness of the filaments assists in sweeping out the pollen at the exact moment of the insect visit. Regular self-pollination is found e.g. in Senecio vulgaris; wind-pollination e.g. in Artemisia and the plants related to it.

This extremely natural and well-defined order is the largest (and no doubt one of the youngest?); it embraces 10–12,000 known species (in 770 genera), or about one-tenth of all Flowering-plants. They are distributed over the whole globe, but are most numerous in temperate countries; the majority prefer open spaces; a smaller number are forest-forms. They abound especially in open districts in America.

Among the substances frequently found may be mentioned: INULIN (especially in the subterranean parts), BITTER materials, Tannin, volatile oils, fatty oils in the fruits. MEDICINAL: “Herba” of Artemisia absinthium (Wormwood) and maritima[+] (Sea-wormwood), Achillea millefolium; the leaves of Cnicus benedictus and Tussilago farfara; the unopened capitula of Artemisia maritima, var. stechmanniana; the capitula of Tanacetum, Matricaria chamomilla[+] (wild Chamomile), Anthemis nobilis[+] (common Chamomile); the separate flowers of Arnica; the roots of Arnica montana[+], Taraxacum officinale[+], Anacyclus officinarum[+], Lappa major, minor, nemorosa and tomentosa, Inula helenium and Artemisia vulgaris; the latex of Lactuca virosa[+]. The following are cultivated for food:--Lactuca sativa (Lettuce), Cichorium endivia (from E. Asia, for salads), Cynara scolymus (Artichoke, Mediterranean), Scorzonera hispanica (S. Eur.), Helianthus tuberosus (Jerusalem Artichoke, from N. Am., introduced into Europe 1616), Cichorium intybus (roots as “chicory,”) Tragopogon porrifolium (Salsafy), Artemisia dracunculus. OIL is extracted from the following (the seeds): Helianthus annuus (Peru), Madia sativa (Chili), Guizotia oleifera (Abyssinia). DYES from: Carthamus tinctorius (Safflower, used in the preparation of rouge; Egypt), Serratula tinctoria. INSECT-POWDER from: Pyrethrum cinerariifolium (Dalmatia) and roseum (Persia, Caucasus). The following are cultivated in houses and gardens for the sake of their scented leaves:--Tanacetum balsamita (Balsam), Artemisia abrotanum (Southernwood) and A. argentea. A great many of the genera enumerated are cultivated in dwelling-houses for the sake of the flowers; e.g. Pericallis cruenta (generally termed “Cineraria”). Asteriscus pygmæus is supposed to be the genuine “Rose of Jericho”; the involucral leaves envelop the fruits after their ripening and keep them enclosed for 8–10 months until rain occurs.

APPENDIX ON THE CLASSIFICATION OF PLANTS.

BY M. C. POTTER.

The earliest systems of classification were derived from the properties and uses of plants; and it was not until some two centuries ago that any scientific grouping of plants was attempted. Aristotle and Theophrastus had adopted the groups of Trees, Shrubs and Herbs as the chief divisions of the Vegetable Kingdom, a system which persisted and was employed by Tournefort and Ray as late as the end of the 17th century. The arrangement by which these three divisions were separated into smaller divisions was often founded upon a single character, such as the formation of the corolla, the form of fruit, that of the calyx and corolla, etc. All these systems of classification which brought into close proximity plants distinguished by some one character alone, could only be considered as artificial, since plants related to one another would not necessarily be included in the same group. As the knowledge of the morphology, physiology, and reproduction of plants increased, such systems were recognised as unscientific, and it became the aim of botanists to establish a natural system, founded upon mutual relationships, which would associate together only those plants which are truly allied.

The following are some of the chief systems of classification which will show the gradual development of the natural system, and may be of service to students making use of this text-book.

System of JOHN RAY (1703).

I. Herbæ. A. IMPERFECTÆ (Flowerless). B. PERFECTÆ (Flowering). Dicotyledones. Monocotyledones. II. Arbores. A. Monocotyledones. B. Dicotyledones.

Ray was the first botanist who recognised the importance of the one or two seed-leaves of the embryo, and initiated the division of the Flowering-plants into Monocotyledons and Dicotyledons.

System of LINNÆUS (1733).

In his well known artificial system Linnæus divided the Vegetable Kingdom into twenty-four classes, based upon the number, relative position and union of the stamens with regard to each other, and also to the gynœceum.

Class I. MONANDRIA. Flowers with 1 stamen. „ II. DIANDRIA. „ „ 2 stamens. „ III. TRIANDRIA. „ „ 3 „ „ IV. TETRANDRIA. „ „ 4 „ „ V. PENTANDRIA. „ „ 5 „ „ VI. HEXANDRIA. „ „ 6 „ „ VII. HEPTANDRIA. „ „ 7 „ „ VIII. OCTANDRIA. „ „ 8 „ „ IX. ENNEANDRIA. „ „ 9 „ „ X. DECANDRIA. „ „ 10 „ „ XI. DODECANDRIA. „ „ 11 to 19 stamens. „ XII. ICOSANDRIA. „ „ 20 or more stamens inserted on the calyx. „ XIII. POLYANDRIA. „ „ 20 or more stamens inserted on the receptacle. „ XIV. DIDYNAMIA. Stamens didynamous. „ XV. TETRADYNAMIA. „ tetradynamous. „ XVI. MONADELPHIA. Filaments united into 1 bundle. „ XVII. DIADELPHIA. „ „ „ 2 bundles. „ XVIII. POLYADELPHIA. „ „ „ several bundles. „ XIX. SYNGENESIA. Anthers united together. „ XX. GYNANDRIA. Stamens and pistil united. „ XXI. MONŒCIA. Flowers diclinous, ♂ and ♀ on the same plant. „ XXII. DIŒCIA. „ „ ♂ and ♀ on different plants. „ XXIII. POLYGAMIA. ♂-, ♀-, and ☿-flowers on the same plant. „ XXIV. CRYPTOGAMIA. Flowerless plants (Ferns, Mosses, Algæ, Fungi).

These classes were further divided into orders, according to the number of styles, as Monogynia, flowers with 1 style; Digynia, with 2 styles, etc. Thus a Dock (Rumex), having 6 stamens and 3 styles, would be placed in Class VI., HEXANDRIA, and Order III., Trigynia.

Class XIV. was divided into two orders. Order I., Gymnospermia, with seeds apparently naked, comprising the Labiatæ; and Order II., Angiospermia, with the seeds enclosed in a capsule (Bartsia, Rhinanthus).

Class XV. was divided into two orders: Order I., Siliculosa, fruit a silicula (Capsella); and Order II., Siliquosa, fruit a siliqua (Brassica).

Class XIX. was divided into Order I., Æqualis, all the flowers perfect (Sonchus); Order II., Superflua, flowers in the centre perfect, those at the circumference with pistils only (seemingly superfluous), e.g. Aster; Order III., Frustranea, flowers in the centre perfect, those at the circumference neuter, e.g. Centaurea.

“Fragments” of a natural system have also come down to us from Linnæus, who himself always recognised the imperfection of his artificial system.

System of ANTOINE LAURENT DE JUSSIEU (1789).

Class =Acotyledones.= Plants without cotyledons: Fungi, Ferns, Mosses, Algæ, Naiades I.

=Monoctyledones.= Plants with one cotyledon:-- 1. Stamens hypogynous II. 2. „ perigynous III. 3. „ epigynous IV.

=Dicotyledones.= Plants with two cotyledons:--

{ Stamens epigynous V. 1. APETALÆ { „ perigynous VI. { „ hypogynous VII.