STRUCTURE OF THE SEED. 219 



nous, on the contrary, the cotyledons are thin and membrana- 

 ceous, retaining in a great measure the appearance of leaves, 

 in the midst of the surrounding albumen. 



At the period of germination the cotyledons separate from 

 the integuments of the seed, and either appear above the 

 ground, different in form from the other leaves of the plant, or 

 they remain hidden in the earth without showing themselves, as 

 in the pea and the horse chesnut, until they finally decay. In 

 the former case, th^y are epigeal [iiti, upon or above, and yia 

 the earth;) in the latter case they are hypogeal (in6 under.) 



The gemmule, is the little bud at the summit of the plumule. 

 Like all other buds, it is composed of a little axis continuous 

 with that of the embryo, and certain minute rudimentary 

 leaves which represent the first leaves which the embryo is 

 going to develope. In general, in Dicotyledons the gemmule 

 is placed between the two cotyledons, which in being applied 

 one against the other, cover and hide it completely. It is 

 therefore necessary to separate the cotyledons in order to see 

 the gemmule. In Monocotyledons embryos, the plumule is 

 absent and the gemmule is placed within the sheathing base of 

 the cotyledonary leaf, and situated as it were, on one of its 

 sides. In developing, the gemmule gives birth to the aerial 

 portion of the stem, and its unfolding rudimentary leaves soon 

 take in succession the form, position and size of those leaves 

 which are peculiar to the adult plant. 



