274 



BOTANY. 



Sub-Class II. The Dicotyledons {Dicotyledonem). 



519. The first leaves of the embryo are two and oppo- 

 site; hence they are said to have two cotyledons. The 

 venation of the leaves is for the most part such that the 

 veins are rarely parallel, and in joining one another they 

 form an irregular network. 



The germination of Dicotyledons may be illustrated 



Fig. 161. 



Fig. 162. 



Fig. 161.— Windsor Bean (Vicia faba). A, seed with one cotyledon 

 removed ; c, cotyledon ; /c?i, plumule ; U', root ; s^ seed-coat. U, germinat- 

 ing seed ; s, seed-coat, partly torn away at I ; st^ stalk of one of the coty- 

 ledons ; K curved stem ahove, and he, short stem (hypocotyl) helow, the 

 cotyledons ; /!, ws, root. 



Fig. 163.— Castor-oil Plant (Riclnus communis). I, longitudinal section 

 of the ripe seed. II, germinating seed with the cotyledons still inside of 

 the seed-coat (shown more distinctly in A. and B). «, seed-coat ; e, endo- 

 sperm ; c. cotyledon ; he, stem (hypocotyl); mi, root. 



by the following examples. In the seed of the Windsor 

 Bean (Fig. 161) the embryo entirely fills up the seed-cavity. 



