WALDRON— THE PEANUT 323 



dark. This was possibly due to a greater drying out in light in 

 her experiments. No normally produced tip hairs were observed. 



Temperature. Plants with roots exposed were kept at 90° F. 

 to 100° F. in a moist chamber. Others were kept at 60° F. to 70° F., 

 the other conditions being the same. Rosette hairs appeared on 

 all the plants, but at the higher temperature they were much more 

 luxuriant and abundant. Tip hairs were found near the tips of 

 several roots on two of the plants growing at the high temperature. 

 These two plants producing both types of hairs were the most vig- 

 orous of the set of twenty in the experiment. These results do not 

 correspond with those of Snow, where a high temperature and hu- 

 midity retarded their growth. This can possibly be explained by 

 the fact that the peanut requires a higher temperature for optimum 

 growth than those plants with which she experimented. 



Soil. Plants in loose sandy soil composed of one-half light loam 

 and one-half sand grew vigorously. After germination they pro- 

 duced numerous long and almost pure white roots, a few of which, 

 after reaching the side of the pot or box, bore a limited number of 

 tip hairs. No rosette hairs appeared until the plants were one to 

 two weeks old and quite well established. Tip hairs appeared on 

 one plant only, of those that were older than three weeks. Plants 

 in light loam, without any mixture of sand, grew slowly and the 

 rosette hairs were the first and only type observed, after the side 

 roots had developed. They appeared on all the plants examined 

 after from one to two weeks' growth. Tip hairs were observed on 

 a two months' old plant which had been retarded in its growth, 

 and, when repotted, a few delicate roots appeared which bore a 

 very few scattered tip hairs.* Rosette hairs could be found on any 

 plant of any age, except the young vigorous specimens of less than 

 two or three weeks' growth. 



On seedlings of various ages no hairs of either sort were ever ob- 

 served on the primary root. Many seeds germinated in sandy soil, 

 and on sterilized wet cotton in test tubes, did not produce them even 

 under optimum conditions of heat, air and moisture. With sufficient 

 moisture, however, rosettes always appeared on the bases of the 

 side roots. Those in test tubes grew slowly because of lack of 



*0f about fifteen such plants examined this one was the only one in which 

 they were observed. 



