DAMPINC-OFF IX FOltl'ST XruSKlIFES. 53 



The results in general make it appear that the Pythhim was able to 

 kill some pines both before and after their appearance above the soil 

 surface on the soil treated with the acid and lime. The control in 

 this experiment did not receive the nutrient substratum added with 

 the Pythium inoculum, but an experiment run under the same con- 

 ditions at nearly the same time, in which seven strains of hyphomy- 

 cetes with the same substrata entirely failed to decrease survival, 

 indicates that the rice subtratum was not in itself the cause of the 

 observed result. The rather weak action of the Pythium in these 

 experiments stands out in sharp contrast to the results with Corticium 

 vagum in the same experiments, practically all emergence being pre- 

 vented by most of the Corticium strains used, some of which had 

 proved less active than Pythium in tests on autoclaved soil. 



In a soil in Nebraska, somewhat similar but with more humus, 5.5 

 c. c. (three-sixteenths fluid ounce) of sulphuric acid per square foot 

 applied in solution at the time of sowing had been found greatly to 

 decrease damping-off. In different parts of beds treated with acid 

 from 10 to 17 days earlier, 96 plats, each 3 inches square, were laid 

 out, and each plat was inoculated at the center. Interspersed with 

 these were 96 plats set apart as controls. Emergence had already 

 begun at the time of inoculation. Jack pine, red pine, and Corsican 

 pine were the hosts, and three Pythium strains of known parasitism, 

 growing in pieces of prune agar the size of peas, constituted the 

 inoculum. The damping-off after emergence was less than 1 per 

 cent higher for the inoculated plats than for the controls. Even such 

 a light inoculation would probably have given some results in auto- 

 claved soil, so the experiment indicates, as would be expected, that 

 this acid-treated soil was less favorable for Pythium debaryanum 

 than steamed soil. 



On pots containing entirely untreated soil the following series of 

 inoculations were made at the time of sowing the seed : 



Inoculation at one point in each pot : 



Experiment 25. Jack and western yellow pine, 1 pot of each inoculated ; 

 survival 13 days after emergence slightly greater in both than in the 

 six controls. 



Experiment 27. Jack pine, 73 pots, 27 controls; average emergence, 59 

 in inoculated pots and 56 in controls; damping-off, 39 per cent in 

 inoculated pots and 37 per cent in controls. 



i:\periment 29. Jack, Corsican, and western yellow pine, 112 plats in- 

 oculated just as emergence commenced instead of at seed sowing, 

 us in other cases, and 112 controls alternating with them ; damping- 

 off was less in the inoculated plats than in the controls. 



Experiment 31. Jack pine, 8 pots inoculated, 8 controls; inoculated, 

 emergence 33 per cent, damping-off 13 per cent, survival 198 ; con- 

 trols, emergence 38 per cent, damping-off 26 per cent, survival 196. 



Experiment 58A. Jack pine, 5 pots inoculated, 5 controls; inoculated, 

 emergence 59 per cent, damping-off 32 per cent, survival 40 ; controls, 

 emergence 51 per cent, damping-off 12 per cent, survival 45. 



