862 
Journal of Agricultural Research voi. xxxu, no. u 
The root systems of both the inoculated and control series of plants 
were excavated and studied at the maturity of the crop. Trenches were 
dug across the adjoining rows of the inoculated and control series in the 
March 31 and May 10 plantings, after which a gentle stream of water was 
used to wash the soil away from the roots. In this way a comparison 
was obtained, not only of the general root development but also of the 
root distribution. The development of lateral feeder root branches, the 
depth of root penetration, and the comparative root development in the 
two different seedings, as well as the influence of the fungus on reducing 
the root system, are shown in Plate 6, A, B, and C. The roots penetrated 
much deeper and developed more lateral branches in the early seedings 
which were grown at a low soil temperature. Likewise, the parasite did 
not reduce the size of the root system at the low temperature, but the 
roots of the inoculated plants in the later seeding at high soil temperature 
were reduced nearly 50 per cent below those of the control plants. 
EXPERIMENTS IN 1921 
Three sowings made on March 19, March 26, and April 11, germinated 
before the average mean soil temperature for the germination period was 
above 12 0 C. The mean daily soil temperature for several days at a time 
during these three periods, however, was above 12 0 . The next two 
seedings, made on April 29 and May 20, germinated at an average mean 
soil temperature considerably above 12 0 , whereas the last seeding, on 
June 20, germinated during a fairly high mean soil temperature and fairly 
high maximum soil temperature. 
