DA 2 BEEMBENTARY BOTANY. 
should be noticed between the apex of the radicle and the © 
black scar; through this the radicle pushes its way out. A 
bean which has been soaked for twenty-four hours will be 
considerably larger than it was in the dry condition, owing 
to the water taken in; and the testa, which in the dry 
condition was wrinkled, is now tightly stretched. 

Fic. 1.—Bgan Seep (ExTERNAL). Fic. 2,—EmBryo oF BEAN. 
 t, testa ; s, scar of attachment of seed stalk; m, hole through which 
radicle protrudes (micropyle) ; ~, plumule ; 7, radicle ; stk, stalk of coty- 
ledons (c). 
The testa may be removed by cutting it along the convex 
side of the bean. It will then be seen that the greater part 
of the seed is occupied by two thick, fleshy lobes ; these are 
the cotyledons ; they are the first leaves of the young plant, 
and in this case contain the food for the young seedling. The 
cotyledons easily separate, and if held apart without breaking 
them, as in Fig. 2, it is possible to make out a yellowish 
structure continuous with the radicle and lying between the 
two cotyledons. This is the plumule, which will give rise to 
the young shoot. The plumule, therefore, is the first bud of 
the plant. <2, 
The radicle, plumule and cotyledons together form the 
embryo, so that the bean seed contains nothing but the young 
plant. | ? 
The time required for the development of radicle and 
