60 



STRUCTURAL BOTANY. 



and leaves (cotyledons). But these parts are sometimes quite 

 undistinguishable until germination, as in the Orchis tribe. 

 The Radicle is the descending part of the embryo, always point- 

 ing toward the micropyle, the true vertex of the seed. The 

 Plumule is the germ of the ascending axis, the terminal bud, 

 located between or at the base of the Cotyledons. These are 

 the seed-lobes, the bulky farinaceous part of the embryo, des- 

 tined to become the first or seminal leaves of the young plant. 

 The nutritive matter deposited in the seed for the early suste- 

 nance of the germinating embryo, is found more abundant in the 

 cotyledons in proportion as there is less of it in the albumen 

 often wholly in the albumen (Wheat), again all absorbed in the 

 bulky cotyledons (Squash). 



181. The number of the cotyledons is variable; and upon this 

 circumstance is founded the most important subdivision of the 

 Flowering Plants. THE MONOCOTYLEDONS are plants bearing 

 seeds with one cotyledon ; or if two are present, one is minute 

 or abortive. Such plants are also called ENDOGENS, because 

 their stems grow by internal accretions ( 421). Such are the 

 Grasses, the Palms and Lilies, whose leaves are mostly con- 

 structed with parallel veins. 



216 



214 



214, Dicotyledonous (Bean). 215, Monocotyledonou* (Wheat). 21G, Polycotyledontus (Pine). 217, 

 Acotyledonous (zoospore of one of the Confervae). (r, r, r, radicle; p, p, p, plumule; c, c, c, cotyledon; 

 a, albumen.) 



182. THE DICOTYLEDONS are plants bearing seeds with two 

 cotyledons. These are also called EXOGENS, because their sterna 

 grow by external accretions ; including the Bean tribe, Melon 

 tribe, all our forest trees, etc. These are also distinguished at a 



