The Acorn germinates in a similar manner, as already shown in _fig._ 86 in p. 192. [Illustration: FIG. 129.—YOUNG PLANT OF HORSE-CHESTNUT.] [Illustration: FIG. 130.—SCARLET HORSE-CHESTNUT.] [Illustration: FIG. 131.—YELLOW HORSE-CHESTNUT.] The flowers of the different species of Æsculus vary considerably; as, for example, in the Scarlet Horse-chestnut (_Æ. rubicunda_), the calyx is tubular (see _a_ in _fig._ 130), and there are but four petals, the upper two of which (_b_) are narrower than the lower ones (_c_), and have bearded claws. This species has sometimes eight stamens. In the Yellow Horse-chestnut, or yellow flowered American Buckeye, the upper petals (_a_ in _fig._ 131) are very much smaller than the lower ones (_b_), and both have very long claws. There are four petals, which conceal the stamens, of which there are frequently only six. The seed of Pavia has only a small hilum, which resembles the pupil of an eye (see _fig._ 132); and hence the genus has received its American name of Buckeye. In one species (_P. macrostachya_), the nut is eatable, and very much resembles that of a Sweet Chestnut when boiled in milk. The stamens in this species are much longer than the petals, and they give a peculiarly light and elegant appearance to the flowers; which, unlike those of the other species, do not appear till the latter end of summer or autumn. [Illustration: FIG. 132.—NUT OF THE BUCKEYE.] ORDER XLVI.—RHIZOBOLEÆ—THE CARYOCAR TRIBE. Trees of large size, natives of tropical America. _Caryocar nuciferum_ produces the Suwarrow, or Butter-nut of the fruiterers’ shops. ORDER XLVII.—SAPINDACEÆ.—SOAP-TREE TRIBE. The only plant in this order which will grow in the open air in England is _Kölreuteria paniculata_, a beautiful tree, with very elegant leaves, and panicles of yellow flowers, which are succeeded by a bladdery capsule, which is divided into three cells in its lower part, though it is only one-celled above. The rind and pulp of the fruit of _Sapindus Saponaria_ are used as soap in those countries of which it is a native. The nuts of this plant are round and hard, and of such a shining black that they are made into buttons and beads by the inhabitants of Spanish America. The whole plant, if thrown into ponds containing fish, will intoxicate, and sometimes kill them. Another interesting plant belonging to this order is the Chinese fruit called Litchi (_Euphoria_ or _Nephelium Litchi_); which has its sweet eatable pulp enclosed in a kind of nut, much wrinkled on the outside; so that the fruit lies within the stone, instead of being on the outside of it. These hard, stone-like berries grow in loose racemes. ORDER XLVIII.—MELIACEÆ.—THE BEAD-TREE TRIBE.