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 
Ftc. 103. — Development of a Red Clover seedling. A, cotyledons being 
pulled out of the ground by the hypocotyl (h); 7, radicle; a, root hairs; ¢, 
testa; c, cotyledons; g, ground line. B, a more advanced stage, showing some 
development of the plumule (p); 8, 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 
