2O 



TECHNICAL BULLETIN 17 



used. Fluctuations occurred in the different cups at any one tempera- 

 ture. The results given in Table VII are typical. The percentages 

 given in the table represent the average of several counts. 



TABLE VII 

 SPORE GERMINATION OF H. sativum IN REDISTILLED WATER AT VARIOUS TEMPERATURES 



In a second series, using hanging drops in petri dishes, 67 per cent 

 of the spores germinated at 6, 54 per cent at 12, 79 per cent at 18, 

 91 per cent at 22, 72 per cent at 28, 91 per cent at 29-30, 80 per 

 cent at 32, 82 per cent at 35, and 87 per cent at 39. 



In a third and fourth series in watch crystals, the spores were not 

 counted but the germination was indicated as poor, moderate, and 

 good. . After 24 hours incubation, in these series, the germination 

 was poor at 6, moderate to good at 12, 18, and 22, and good at 

 the higher temperatures. By count, 89 per cent of the spores germinated 

 at 39. At the end of 48 hours the germination was good at 6. 



From these results with redistilled water it is difficult to detect 

 any quantitative effect of temperature on the number of spores which 

 germinate. Even at i C. a small number of spores will germinate. 

 This, however, is probably very near the lower limit. At the lower 

 temperatures, i, 6, and 12, pieces of mycelium in the cultures 

 always germinated much more readily and sent out longer tubes than 

 did the spores. At 40-42 no germination occurred in the first series 

 for which the results are given. In later series, however, high germi- 

 nation sometimes occurred at 38-39. Comparing these results with 

 the data presented in Table V, we find 35-39 to be the maximum 

 temperature for the growth of the mycelium on potato dextrose. At 

 temperatures as high as 35 and 39 the germ tubes appeared very 

 quickly, but were always short and did not increase much in length 

 after two or three days. On the other hand, at 22, 28, and 32, 



