PHYSIOLOGY AND MINERAL NUTRITION 97 



grown in containers, but not when grown under field conditions. Failure 

 to find hairs on the latter was thought to result from washing them ofif in 

 the excavation process. It has been reported (3) that the epidermis of 

 the roots of peanuts in the seedling stage sloughs ofif and typical root 

 hairs are not produced, although peculiar tufts of hairs form at the base 

 of most of the branch roots. Conversely, Bruner (17) indicated that root 

 hairs were plentiful on the absorbing rootlets of the field plants he 

 studied. Since the roots of peanuts are fragile, it is possible that the root 

 hairs in many cases may have been lost in the harvesting process. If, 

 however, peanuts have very few root hairs, as many believe, the major 

 portion of root absorption would be through channels other than root 

 hairs. 



In summary, the plant has an extensive root system, the branches 

 sometimes have adventitious roots, the gynophores produce root-hair-like 

 outgrowths, and the fruit develops in the soil and sometimes has forma- 

 tions similar to root hairs on the shell. Nutrients could be absorbed by 

 each of these organs. 



WATER AND OXYGEN RELATION 



The peanut is classified as a mesophytic plant but has xerophytic 

 tendencies since it grows well in areas of Texas (68) and other States 

 which may be considered as a transition zone between the mesophytic east 

 and the xerophytic western plains. 



Peanuts are usually grown on well-drained soils which are frequently 

 sandy in nature. This ecological relationship suggests that liberal amounts 

 of oxygen might be beneficial and that excessive moisture is not desirable 

 for best development of peanuts. Shibuya (74) indicated that oxygen in 

 the pegging area is necessary for fruit production, but the amount re- 

 quired was not determined. However, data relative to drought resistance, 

 water and oxygen requirements of the peanut plant are not available so 

 far as the writers are aware. 



It is usually assumed that water enters plants largely through the 

 root hairs. If peanuts have few root hairs, then water absorption would 

 have to be by other means. As stated previously, adventitious roots, 

 root-like hairs on pegs and sometimes on shells of fruit, may be present, 

 but the relationship of those structures to water absorption has not been 

 established. However, it has been shown that pegs and developing fruit 

 do absorb some mineral elements (9, 19, 84). It is assumed that water 

 movement through the peanut plant would be similar to that of most 

 other plants. 



