MORPHOLOGY, GENETICS AND BREEDING 



41 



The basic morphological pattern of the epicotyl is laid down in the 

 seed. Its main axes consists of a central stem and two cotyledonary lat- 

 erals ( figure 10) . Contrary to the situation in many plants, at least after 

 the first 3 weeks, the main axis of the shoot exerts little inhibitory efifect 

 on lateral axes. The main axis develops first but is soon equalled in 

 length by each of the two cotyledonary laterals, and eventually may be 

 much exceeded by them. From the beginning the plant is provided with 

 three active shoot apices. The third and fourth lateral axes arise from 

 the central stem subtended by its first two foliage leaves. These no doubt 

 are the four branches described by Bouffil (13) but two of them appear 

 much later than he indicates. In Virginia type peanuts additional vege- 

 tative branch axes commonly arise from the first two nodes of each 



Figure 9. — Cotyledon from 24-day old peanut seedling, cross section. Stored food 

 material absent, tissues collapsed and beginning to disintegrate, (after Yar- 

 brough, 76.) 



