MORPHOLOGY, GENETICS AND BREEDING 45 



So far as is known these structures have not been put to practical use 

 by rhan. 



The root system in A. hypogaea consists of a tap root with many 

 laterals (figures 10 and 12) and adventitious roots from the hypocotyl 

 and aerial branches. The nature of the much-branched and vari-formed 

 adventitious roots developing from the bacterial nodules (Prevot, 54) 

 has not been clarified.* Prevot suggested certain possible functions for 

 such roots but these have not been experimentally verified. Some of the 

 wild species fr equently d evelop extensive branching roots from the pegs 

 (Gregory, 27). A.Ji^^ogaeaJhasheen observed to do this occasionally 

 but in s uch cases the roots canjjsually be seen to develop from callus 

 tissuejoUowmgjwounding of the peg or pod. The development of root 

 hairs has not been studied sufficieritTy in A. hypogaea or at all in the 

 wild species. 



Stems' 



The cultivated peanut is ordinarily (1) erect (bunch) or (2) pros- 

 trate (running) although intermediate growth forms occur. In both cases 

 there is an erect primary branch which serves as the axis of the plant and 

 gives rise to various lateral branches. The central axis (rnain stem) de- 

 velops from the terminal bud of the epicotyl and is flanked by two oppo- 

 site, lateral branches which arise from the respective cotyledonary axils. 

 The central axis is always erect but may be relatively short in the pros- 

 trate varieties. In the erect varieties the lateral branches are also erect 

 or ascending, but even in these types the plants may become semi- 

 decumbent as growth proceeds. In contrast, the main lateral branches of 

 the truly prostrate vai^ieties always grow peripherally from the main axis 

 and usually lie within an inch of the ground except at their tips, which 

 may be somewhat ascending. 



Working with cuttings, Harvey and Schultz (29) observed in an 

 erect type that main stem and lateral cuttings produced plants which 

 were essentially similar in flowering habit to the control plants grown 

 from seed. In two other varieties, characterized by non-flowering main 

 stems, the main stem cuttings produced no flowers on the original axis 

 but produced laterals in a manner comparable to the seedlings. The cut- 

 tings of the laterals continued to behave as laterals, however, and pro- 

 duced inflorescences on all branches including the initial axis which 

 had been cut from the parent lateral. One of these varieties was distinctly 



* In his figure 13, Prevot (54) illustrated a cluster of these roots on which the nodules pro- 

 duced a number of white rootlets, having the appearance of roots grown under the influence of 

 heteroauxin. These rootlets were thickened, short, and often had claviform ends. It may be 

 noted that these roots appear very similar to those infested with nematodes. 



