SEEDLINGS OF THE PEA TYPE 



109 



the stem. In some plants, as in Red Clover and Alfalfa, the 

 radicle forms a prominent tap-root which enables the plant to 

 penetrate deeply into the soil in its adult stage. 



In the Morning Glory, where the stem called the vine may be 

 many feet in length, there is extreme elongation of the plumule. 

 On the other hand, as in some Clovers and Alfalfa, the plumule and 

 hypocotyl form a short thick stem, called the crown, which is barely 



Fig. 103. — Development of a Red Clover seedling. A, cotyledons being 

 pulled out of the ground by the hypocotyl {h); r, radicle; a, root hairs; t, 

 testa; c, cotyledons; g, ground line. B, a more advanced stage, showing some 

 development of the plumule (p); b, first real leaf; d, second real leaf. C, a 

 later stage, showing that the plumule has formed more leaves (e) but has 

 elongated very little. 



above the surface of the ground, and from which the branches 

 arise that bear the leaves, flowers, and fruit. {Fig. 103.) 



Seedlings of the Pea Type. — The seedlings of the Pea and 

 Scarlet Runner Bean represent those dicotyledonous seedlings in 

 which the hypocotyl remains short. Thus the cotyledons remain 

 underground and the plumule is pushed to the surface by the 

 elongation of the stem of the epicotyl just as occurs in the Grass 

 seedlings. But in these seedlings, in contrast to those of the 



