204 Studies of Plant Growth in Heated Soil [Jan- 



attention was given to these, it may be mentioned in this connection 

 that the most abundant were Pyronema and a species of Moiiilia. 

 A racemose species of Mucor appeared in one pot. These fungi 

 did not appear to interfere with the germination of the buckwheat 

 or of the small grains used in the other experiments of this series. 

 The fungi were always more abundant on the soil which had been 

 heated to the higher temperatures, while none appeared on the 

 check pots. 



Experiment ii. JJlieat. The first planting of wheat was 

 allowed to grow about twelve days before being photographed 

 (Fig. 5). The plants in all the pots showed good growth, there 

 being a slight advantage with the check in vigor and color, while that 

 in the soil which had been heated to the lowest temperature (95 ) 

 was almost as healthy and vigorous. In the two high temperature 

 pots the growth was very rank and weak. Although not quite so tall, 

 the plants in these two pots fell down or " lodged " considerably in 

 the 1 35 pot, and very noticeably so in the 175 pot. The plants in 

 these two pots behaved much as does grain grown on a soil too rich 

 in humus. The later growth of this series, while not photographed, 

 was quite interesting. The two low-temperature pots (check and 

 95 ) were almost equal in growth and vigor, the 95 ° one having a 

 slight advantage in vigor and color, but not outgrowing the check 

 in height. The other two pots remained stunted and, after the lapse 

 of a month, showed appreciable inhibition as compared to the others. 

 Indeed, the one which had been subjected to the highest temperature 

 grew but little in height after the second week. This work was 

 twice repeated with results similar to those just described. 



One of these series was photographed at about five days after 

 germination (Fig. 4). The plants on soil which had been heated to 

 95 showed a very slight advance over the check in color, but not 

 quite such a good growth. The pot which had been subjected to a 

 heat of 1 35 showed some retarded germination, giving a very 

 uneven growth, while that subjected to a temperature of 175 was 

 markedly retarded, showing only a slight growth as compared with 

 the others. The work on wheat was seriously interfered with by 

 rust (Puccinia graminis) and mildew (Erysiphe graminis), both 

 of which attacked the weakened plants on the soils which had been 

 heated to the higher temperatures in preference to the more vigor- 



