A Study of Meadow-Crop Diseases in New York 



83 



TABLE 21. Effect of Temperature on Conidial Germination of Heterosporium 



Phlei 



It is evident that ordinary spring and summer temperatures are satis- 

 factory for germination of the spores, since they seem to germinate prac- 

 tically as well at 3° as at 25° C. Temperatures of 30° and 35° C. appear 

 to be too high for the best germination. More time for germination at 

 the lower temperature levels might have allowed more germination of the 

 spores. 



In both cases the spores were allowed to remain on the slides for forty- 

 eight hours before making germination counts. This was to make sure 

 that all the germinable spores had grown; but as time curves for the 

 various temperatures were desirable, another experiment was made to 

 provide the necessary data. 



It is shown in figure 18 that germination occurs equally well at 25° 

 and 3° C, but it was predicted that the curve for 3° would show a lag 

 behind the curve for 25°. Accordingly, a series of slides of the same spore 

 suspension was prepared and placed in moist chambers at the two tem- 

 peratures, 3° and 25°. Two slides were removed from each incubator at 

 intervals of two hours, and the amount of germination was recorded. 

 The results of the experiment are presented in table 22. 



TABLE 22. Effect of Time upon Conidial Germination of Heterosporium Phlei 



at 3° and 25° Centigrade 



Hours 

 elapsed 



3° Centigrade 



25° Centigrade 



Total 

 number 

 of spores 



Per cent 

 of germina- 

 tion 



Total 

 number 

 of spores 



Per cent 

 of germina- 

 tion 



9 a.m 

 1 1 a.m 

 1 p.m 

 3 p.m 

 ."> p.m 



7 p.m 

 9 p.m 



10 p.m 



8 a.m 



10 

 12 

 14 

 23 



No germination 



448 

 426 

 262 

 503 

 445 

 501 

 541 



2.2 

 5.0 

 10.3 

 30.1 

 45.8 

 55.7 

 84.0 



No germination 



580 

 ).')!> 

 491 

 481 

 446 

 450 

 473 



23.6 

 70.6 

 85.7 

 89 9 

 92.6 

 91.8 



