38 DICOTYLEDONS. [CHAP. 



17. Turning back to our first chapter (page 8), we 

 may compare the structure of the seed of the Buttercup 

 with that of the Bean. At first sight they appear to have 

 nothing in common, excepting that each seed encloses an 

 embryo. In the Bean, however, the embryo fills the 

 seed-skin, while in the Buttercup it occupies a very small 

 space at the base of the seed, being enclosed in a uniform, 

 solid substance, which occupies nearly the whole seed. 

 This substance in which the embryo is embedded we 

 called the albumen (Fig. 7), whatever may be its texture 

 or chemical composition. It is at the expense of this 

 albumen that the minute embryo of Buttercup is enabled, 

 during its germination, to develop a root and stem. It 

 originates, like the embryo itself, by free-cell formation 

 in the embryo-sac (p. 20) and may, or may not, be ab- 

 sorbed in the process of maturation of the embryo. If 

 any remain after the seed is ripe, whether much or little 

 in proportion to the size of the embryo, the seed is 

 albuminous. If it be all absorbed before the seed is ripe, 

 so that the seed-coat contains embryo only, the seed is 

 exalbuminous. In exalbuminous seeds, therefore, what- 

 ever nutrient matter may be required to sustain the early 

 stages of germination, is incorporated in the embryo 

 itself. Between the two extremes of abundant albumen 

 in the ripe seed (Buttercup) and no albumen at all (Bean), 

 we have every degree. 



1 8. The embryo of Buttercup requires a magnify ing- 

 *lass for its examination. All that you will be able to 

 make out of it is, that it is slightly notched on its inner 

 side, that is toward the body of the albumen on the side 

 turned from the micropyle. The notch obscurely divides 

 this side of the embryo into two lobes, which are the 

 rudimentary cotyledons. The opposite extremity is the 

 radicle, directed towards the micropyle. The plumule 

 does not develop until after germination, which process, 

 in the Buttercup, agrees generally with that of the Bean ; 

 the albumen serving the purpose of a warehouse of 

 nourishment in the Buttercup, and the fleshy cotyledons 

 the same purpose in the Bean. 



Like the Bean, therefore, the Buttercup is dicotyle- 

 donous ; and as the character expressed by this term (the 

 possession of a pair of cotyledons, or, more strictly, the 



