GEXEEAX MOEPHOLOGY. 



central axis, t, the lower part of which is called the radicle, r ; 

 and its upper extremity, which is terminated by two or more 

 rudimentary leaves, is termed the jphomule or gemmule, n. This 

 axis is united to two fleshy lobes,' c c, whose office is of a 

 temporary nature, and to which the name oi_cotyledons or seed- 

 leaves has been given. Some seeds only contain one cotyledon 

 in~~Their embryo {fig. 16, c), instead of two as just described in 

 the pea {figs. 14 and 15, cc); hence we divide Phanerogamous 

 plants, or those which are reproduced by seeds, into two great 

 classes, called, respectively. Dicotyledons {two cotyledons), and 

 Monocotyledons {one cotyledon). 



When a seed is placed under favourable circumstances (which 

 will be treated of hereafter in speaking of the process of germi- 

 nation) the embryo that it contains begins to develop {figs. 15 and 

 1 6) ; the lower part of its axis or radicle, or one or more branches 



Fig. 15. 



Fig. 16. 



Fig. 15. Germination of the Haricot or French Bean, a Dicotyledonous 

 plant, r. The roots springing from the lower end of the axis, t 



(tigelle). c, c. The cotyledons, d. The leaves. Fig. 16. Germination 



of Maize, a Monocotyledonous plant, t. The axis giving ofE roots 

 from its lower extremity, c. The cotyledon, g. The leaves and young 

 stalk. 



from it, growing in a downward direction, while the upper part 

 elongates upwards, carrying the plumule with it, while at the 

 same time the cotyledonary portion becomes developed and 

 forms the first leafy organs. We have thus produced a central 



