Part 65

Family 16. =Aesculinæ.=

The essential characters of this family are in the main the same as those of the Terebinthinæ and Gruinales. The flowers are hypogynous, perfect, with free petals, 5-merous (S5, P5, typically A5 + 5, all of which, however, are not generally developed; in our native orders there are only 7–8 stamens), and most frequently a 3-merous, 3-locular gynœceum (less frequently 2 or 5 carpels with as many loculi). In each loculus there are usually only 1–2 ovules. A deviation from the preceding families is the frequent zygomorphy of the flower, with, as a rule an oblique plane of symmetry (Fig. 471). When a disc is developed it is placed outside the stamens. The majority have no endosperm (Fig. 473).--The members of the family are nearly all trees.

The family is closely allied to the Terebinthinæ, but unlike this it never has aromatic properties, and differs also in the position of the nectary, in the flowers, which are often irregular with a reduction in the number of stamens, and in the ovule which is usually ascending with micropyle pointing downwards (the Terebinthinæ having the micropyle turned upwards), etc. It is also related to Frangulinæ, the Staphyleaceæ being the chief connecting link; but the Æsculinæ generally have compound leaves.

Order 1. =Staphyleaceæ.= Leaves opposite, often compound. Flowers regular, ☿, 5-merous in calyx and corolla, 5-stamened. The stamens are placed outside the nectary. Ovary syncarpous or 2–3-partite with free styles. The capsule is thin, bladder-like, 2–3-locular, opening at the apex, and has several very hard seeds with a shining testa without aril. Endosperm. Staphylea pinnata (S. Europe) and trifoliata (N. Am.) are cultivated in gardens; they have white flowers in pendulous, axillary racemes or panicles.--16 species.--Staphylea is found in the Tertiary of N. America.

Order 2. =Melianthaceæ.= Glaucous shrubs with scattered, pinnate leaves, and large stipules. Melianthus.--8 species; S. Africa.

Order 3. =Sapindaceæ.= Trees or shrubs, often climbing by tendrils (lianes with anomalous structure of the stem) and with compound leaves. The flowers, in most cases, are small, insignificant, and without scent, and in some polygamous and zygomorphic. S4–5, P4–5, A8 (less frequently 5–10) inside the nectary (disc); ovary generally 3-locular, with 1–2 ovules in each loculus (raphe ventral, micropyle turned downwards). Seed without endosperm, often with an aril. The embryo is often thick and curved (Fig. 473).

FIG. 471.--Diagram of the flower and of a scorpioid cyme.

FIG. 472.--Flower in longitudinal section.

FIG. 473.--Seed in longitudinal section.]

Æsculus (Horse-Chestnut). Trees with opposite, digitate, dentate leaves without stipules; the inflorescence is composed of unipared scorpioid cymes arranged in a pyramidal panicle (termed a thyrsus). The flowers are irregular, with an oblique plane of symmetry (through the 4th sepal, Fig. 471); there are 5 sepals, 5 free petals, of which the one lying between S^3 and S^5 is the smallest (see Fig. 471) and may be absent; stamens 7 (5 + 2), three being suppressed; gynœceum simple, 3-carpellary and 3-locular, with single style; of the two ovules one is ascending, the other descending (Fig. 472).--The fruit is a 3-valvate, sometimes spiny, capsule, with loculicidal dehiscence, the seed having a large hilum, a curved embryo without endosperm and united cotyledons (the radicle lies in a fold of the testa, Fig. 473). Æ. hippocastanum (Greece, Asia), introduced into cultivation about 300 years ago; the majority of the other species, e.g. Æ. pavia, etc., several of which are frequently cultivated in gardens, are from N. America. ~The flower of the Horse-Chestnut is adapted for bees, whose abdomen touches the anthers or style when visiting the flower. The flowers are protogynous.~

The other Sapindaceæ have most frequently 4 sepals, 8 stamens, various fruits (septicidal capsule, nuts with or without wings, schizocarp), etc. Serjania, Cardiospermum, Sapindus, Koelreuteria, etc. (about 118 genera, 970 species). The seeds of Paullinia sorbilis contain caffeine, and are used as “Pasta guaranà,” in the North Western Brazils in the manufacture of a common drink. Nephelium (or Euphoria) litchi (with edible aril), and other species, from Asia.

Order 4. =Aceraceæ.= This order is so closely allied to the Sapindaceæ, that some authorities have classed it with them. The main difference is in the regularity of the flowers, and the =2=-merous gynœceum (in abnormal cases several carpels occur).--They are trees, and, like the Horse-Chestnuts, have opposite leaves without stipules; in Acer the leaves are palminerved, but imparipinnate in Negundo, a plant frequently cultivated in gardens. The flowers are often unisexual, polygamous (some species have ☿-, ♂-and ♀-flowers); sepals 5, petals 5 free, =stamens 8= (that is, 5 + 5, but the two median ones are absent) inside a large disc. Fruit a samara (schizocarp) with 2 winged, nut-like fruitlets (Fig. 474). In each of the 2 loculi of the ovary are 2 ovules. Embryo curved, with thin, folded cotyledons. Endosperm absent.--~The inflorescences are racemes with a more or less elongated main axis and terminal flower (which sometimes has 10 stamens); when the lateral branches are developed they are similar to the main axis. In some species both corolla and petal-stamens are suppressed. Acer is pollinated by insects, Negundo by the wind.--88 species; North Temperate zone. Acer in the Tertiary from the Oligocene. The following are native plants: Maple (Acer campestre), Sycamore (A. pseudoplatanus, doubtful native). Important as avenue trees and timber. Sugar is obtained from the spring sap of the Sugar Maple (N. Am.).~

Order 5. =Malpighiaceæ.= A tropical (especially American) order closely related to the Aceraceæ, having often the same form of fruit (but 3-partite). Some species are lianes with anomalous stem-structure. Leaves opposite. The flowers are regular or obliquely zygomorphic (the plane of symmetry passing through sepal 3), with S5, P5, A5 + 5, G3; 1 pendulous ovule in each loculus. Important characteristics for identification are the numerous grandular structures on the sepals. Peculiar 2-spined hairs are found in some. Malpighia, Bunchosia, Galphimia, Tetrapterys, Heteropterys, etc.--About 600 species.

Order 6. =Erythroxylaceæ.= Sepals 5, petals 5 (with a ligular corona), 10 stamens in one bundle. Gynœceum 3-locular. Fruit a drupe. Tropical (especially American) trees and shrubs, the Coca-plant (Erythroxylon coca) being best known. Its leaves are considered by the inhabitants of Chile and Peru to be one of the indispensable necessaries of life; they are chewed, and possess intoxicating, exhilarating properties, and contain the alkaloid cocaine, which is frequently employed as a local anæsthetic.--103 species; chiefly in America.

Order 7. =Vochysiaceæ.= Trees; Trop. Am. 1 stamen.--140 species.

Order 8. =Trigoniaceæ.= Shrubs; Trop. Am.--30 species.

Order 9. =Tremandraceæ.= Polygalaceæ with regular flowers.--27 species. Australia.

Order 10. =Polygalaceæ.= Herbs or shrubs (some tropical species are lianes) with scattered (rarely opposite), simple and most frequently quite entire leaves, without stipules. The flowers are usually borne in terminal spikes or racemes, and are strongly zygomorphic (the plane of symmetry being median); they have 5 free sepals, the 2 lateral ones of which (4 and 5 in Figs. 475, 476) are very large, petaloid, and frequently project on each side like the “wings” of a Pea-flower; petals 5, of which the two lateral ones are wanting or rudimentary (dotted on Fig. 475), and the anterior “the keel” (Fig. 476 c) is large, hollow and boat-shaped, and frequently with a lobed or fimbriated edge (Fig. 476 A and B, c); stamens 8, the two median ones being absent, all united into a tube split along the back, which is also slightly united to the keel (the anthers, often 2 locular, open by pores, Fig. 476 B, st); the 2 median carpels form a bilocular ovary. 1 pendulous ovule in each loculus (Figs. 476 C, 475); capsule compressed with loculicidal dehiscence, rarely a nut. Polygala (Milk-wort).

470 species; distributed over the whole globe (none Arctic). OFFICINAL: the root of P. senega, from N. Am. Some are used as ornamental plants.

POLLINATION. The flowers of Polygala are pollinated by insects (chiefly bees). The fimbriated processes of the anterior petal support the insect when it alights. The anthers lie on each side of the stigma in the pouch of the anterior petal; the apex of the style is spoon-shaped, and immediately behind it is a viscid stigmatic lobe. In reaching the honey the proboscis of the insect must come in contact with the pollen and the viscid stigma, by which it is rendered sticky; this ensures the pollen adhering to the proboscis and so being carried to other flowers.

Family 17. =Frangulinæ.=

The plants belonging to this family, with very few exceptions, are trees or shrubs. The leaves are usually simple; stipules may be absent or present. The flowers in almost all the orders are small, green or whitish; they are always regular, 4-or 5-merous with 2–5 carpels, but never have more than 1 whorl of stamens, which in Rhamnaceæ and Ampelidaceæ are placed opposite the petals (typically 5 + 5 or 4 + 4 stamens, of which however either the external or internal whorl is always wanting); hypogynous or slightly perigynous, in Rhamnaceæ only strongly perigynous or epigynous; generally ☿; the calyx is inconspicuous; petals free or slightly united. Gynœceum simple; ovary generally multilocular; style short or entirely wanting. A disc is nearly always developed in the flower, but is found sometimes inside the staminal whorl, sometimes outside it or between the stamens. The ovules are apotropous (anatropous with dorsal or ventral raphe).

Order 1. =Celastraceæ.= Euonymus europæa (Spindle-tree) may be chosen as a type. It is a shrub with simple, opposite leaves and small caducous stipules. The small, greenish-yellow flowers, borne in regularly-branched dichasia, are regular, ☿, with 4 whorls, 4-(or 5-) merous in regular alternation. There is a thick disc upon which the polypetalous corolla (imbricate in the bud) and the stamens are borne, with a slightly perigynous insertion. The style is short and thick; the ovary has 2 erect ovules in each loculus. The fruit is a red, 4-valvate capsule with loculicidal dehiscence; the seeds are few in number, and have a large, red-yellow aril (developed from the micropyle). Embryo green, in a large, fleshy, white endosperm. ~The dingy yellow flowers are generally visited only by flies and ants for the sake of the honey secreted by the disc, and while they run about on the flowers they touch the anthers and stigmas, now with one part of the body, now with another. The flower is protandrous. The stigmas are not developed till several days after the opening of the anthers.--Celastrus, Cassine, Catha, etc.~

38 genera; 300 species. Distributed over the entire globe, with the exception of the colder districts, and especially in the Tropics. Some are ornamental bushes (Euonymus japonica). The leaves of Catha edulis are used by the Arabs and Abyssinians in the same way as those of Coca by the Peruvians.

Order 2. =Hippocrateaceæ.= 150 species; tropical; chiefly lianes. S5, P5, A3, G3. Anthers extrorse.

Order 3. =Aquifoliaceæ (Hollies).= The genus Ilex forms almost the entire order. (175 species out of 180; especially from S. Am.) They are shrubs or trees with scattered, leathery, simple leaves (in Ilex aquifolium, spiny) with very small stipules. The flowers are small, white, and borne in few-flowered inflorescences in the axils of the foliage-leaves; they are most frequently unisexual and diœcious. There are 4–5 sepals, petals, stamens and carpels in regular alternation; the calyx and corolla have their leaves slightly connate; stamens slightly adnate to the corolla; the ovary is generally almost spherical with a thick, sessile stigma (Fig. 477). This order deviates especially from Celastraceæ in the absence of the disc and in having only 1 (pendulous) ovule in each of the 4 loculi of the ovary, and in having a drupe with generally 4 stones. Embryo extremely small, at the apex of the large endosperm, with the radicle directed upwards.--~3 genera.--I. aquifolium (Holly) principally on the coasts of European countries; from Norway to W. Denmark, and further westward. It is a common garden shrub with stiff, shining leaves and red fruits. Several South American species contain so much caffeine that they may be used as a beverage in the place of tea (I. paraguayensis, Paraguay tea, or Maté). The Holly does not contain caffeine.~

Order 4. =Ampelidaceæ (Vines).= Shrubs with the stem swollen at the insertion of the petioles and climbing by tendrils borne opposite the leaves (Figs. 478, 479). The leaves are scattered (generally 1/2), stalked, stipulate, frequently palminerved and lobed, divided or compound. The small, greenish flowers are generally borne in paniculate inflorescences, whose position is the same as that of the tendrils (Fig. 478); they are hypogynous or slightly perigynous, ☿, with 4–5 sepals, petals, stamens (which, as in the Rhamneæ, are opposite the petals; Fig. 480 A, B) and 2 carpels. The calyx is very small, entire, or slightly dentate; corolla valvate, and in some falling off as a hood, since the individual parts remain united at the summit (Fig. 480 A). Between the stamens and gynœceum is situated an hypogynous disc, with 5 lobes alternating with the stamens (Fig. 480 A, B, E). In each loculus of the 2-locular ovary there are 2 erect ovules (E); the style is short or wanting. The fruit is a berry. The embryo is small and lies in a horny, sometimes slightly folded (ruminate) endosperm (Fig. 480 C, D).

FIG. 478.--Branch with bunch of grapes.