. A history of the vegetable kingdom; embracing the physiology of plants, with their uses to man and the lower animals, and their application in the arts, manufactures, and domestic economy. Illus. by several hundred figures. Botany; Botany, Economic; 1855. 104 HISTORY OP THE VEGETABLE KINGDOM. six in taxodium disticlnim; eight in pinus stro- his; and lastly, ten and even twelve in /'!«2«s pinea. It is thus seen that the number of cotyledons is not the same in all plants, and that the divi- sion into monocotyledons and dicotyledons, if strictly observed, is incapable of including all knovifn v
. A history of the vegetable kingdom; embracing the physiology of plants, with their uses to man and the lower animals, and their application in the arts, manufactures, and domestic economy. Illus. by several hundred figures. Botany; Botany, Economic; 1855. 104 HISTORY OP THE VEGETABLE KINGDOM. six in taxodium disticlnim; eight in pinus stro- his; and lastly, ten and even twelve in /'!«2«s pinea. It is thus seen that the number of cotyledons is not the same in all plants, and that the divi- sion into monocotyledons and dicotyledons, if strictly observed, is incapable of including all knovifn vegetables. Besides, it not unfrequently happens, that the two cotyledons unite and ad- here together, so that, at first sight, it is difficult to say whether an embryo is monocotyledonous or dicotyledonous, as, for example, in the horse- chestnut. The cotyledons appear to be destined by nature to favour the development of the young plant, by supplying it with the first materials of its nutrition. For this purpose, the cotyledons are almost always very thick and fleshy, in plants which have no etidospenn, whereas they are thin, and as it were leafy, in those which are furnished with that organ. These differences may easily be seen on comparing the thickness of the cotyle- dons in the kidney-bean and the ricinus com- munis. At the period of germination, the cotyledons sometimes remain concealed under ground, with- out appearing at the surface. In this case, they bear the name of liypogeal cotyledons, as in the horse-chestnut. At other times they emerge. a Oj cotyledons, forminf^ seminal leaves; b, the gemmule ex- panded into primordial leaves; e, tlie radicle. from the ground, in consequence of the elonga- tion of the neck, which separates them from the radicle. In this case, they are named epigeal, as in the kidney-bean and most of the dicotyle- dones. When the two cotyledons are epigeal, or rise above the ground, they form the two seminal leaves. The gemmule is the simple or
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