136 ACADEMIC BOTANY. 



by only one of their united edges (Fig. 191, B) ; II. Conduplicate 



when they bend at base so as to clasp 

 the caulicle by both of their united 

 edges (Fig. 191, C) ; III. Incum- 

 bent when they bend at base so 

 that their midribs are in the same 

 plane with the caulicle; the coty- 

 ledons may be straight (Fig. 191, 

 A) or coiled (Fig. 188, D). 



312. Fleshy Cotyledons characterize 

 most of our nuts. Sometimes the 

 Fig. 193.— a, seed of Ivory-nut (p/iy- two cotyledons are consolidated into 



W«j)ftas nMCrooarpa), showing the aper- -■ tVip TTnrsp r>lipstniit CFiV 



ture (with a circular lid) through °"®' ^^ ^^^ tie Jlorse-cnestnut (J<!g. 



which the small excentric embryo will 192) ; they are then called Confer- 



pass out at germination. B, vert. nee. ruminate (L. conferro, I brine; to- 



of sd. of Custard-Apple (4,,ona Iriioha). ^^^^^^ . ^^^^^^ ^^^^ ^^^^ paunch) ; 



the cotyledon being compared to the dugs of an animal, or to the 

 stomach in which the food is stored. 



313. The Plumule is governed by the laws of both stem 

 and leaf, and is equally instructive and interesting. 



314. The Perisperm is very different in different plants. 



It is farinaceous (floury) in the grains ; corneous (horny) in the 

 Coflee, etc. The Ivory-nut (Fig. 193, A) gets its English name from 

 the appearance and quality of its perisperm ; and it is used for the 

 same purposes as ivory. The perisperm of the Cocoa-nut is the white 

 meat, which is fibrous, hollow, with milk in its cavity, the milk being 

 a part of the perisperm. In the Papaw and Custard-Apple (Fig. 193, 

 B) the perisperm is ruminated; that is, the testa projects into it, 

 making folds like those in the double stomach of an animal that 

 ruminates (chews the cud). The Nutmeg (Fig. 196) is also rumi- 

 nated, from the foldings of the tegmen. The perisperm performs 

 the same office in all seeds ; no matter how firm its texture, it 

 softens when the embryo is ready to sprout ; the greater part of it 

 is changed into sugar, starch, and other substances to feed the grow- 

 ing plant. Seeds with perisperm are termed Albuminous, because 

 formerly the perisperm was called Albumen on account of its position, 

 which resembles that of the albumen (white) of an egg. But it is 

 not at all albuminous in structure, and the term is now discarded. 



315. JExalbuminous seeds have no perisperm. Here the 

 nutriment is stored in the cotyledons (Almond, Walnut, 

 Cream-nut, Yonquapfine) or the caulicle (South American 

 Butternut, Dodder). 



316. The Seed-Coats are as varied as the other parts of 

 the plant. 



317. In the Gymnosperms (except Gnetacese) there is 

 but one seed-coat, and this becomes thick, fruity, and 



