TILLETIA TRITICI 229 



However, numerous experiments go to show that chlamydospores 

 germinate much better in direct contact with the air than when 

 submerged in water. 



It was found that, other things being equal, chlamydospores 

 germinate just as well in diffuse light as in total darkness. 



One of the most important external conditions affecting germina- 

 tion is what, for the present, may be called ventilation. Chlamydo- 

 spores were sown at the surface of a layer of water in a number of 

 Syracuse watch-glasses, and it was found that germination took 

 place far better when the watch-glasses were exposed to the moving 

 air of the laboratory than when they were covered over with large 

 or small bell-jars. 



Syracuse watch-glasses (c/. Fig. 113, A), when placed one above 

 the other, do not fit exactly, so that crevices are left between them 

 and the air can pass in and out of any one of the chambers. 

 Chlamydospores were sown on water in twelve watch-glasses, and 

 of these two stacks of six each were made. One stack was exposed 

 to the air of the laboratory and the other was covered by a large 

 bell- jar set upon a glass plate. After 4-6 days it was found that 

 the spores in the first stack had germinated, whereas those in the 

 second showed no sign of germination. This experiment was re- 

 peated several times, always with the same result. After 8-20 days, 

 in some of the experiments the spores under the bell- jar had still 

 failed to germinate, whilst in other experiments a few of the spores 

 under the bell- jar had germinated. The germ-tubes of these 

 tardily germinating spores did not grow well. 



From the results of the experiments just described we may 

 conclude that ventilation favours the germination of the chlamydo- 

 spores. However, an analysis of the factors included under the 

 term ventilation still remains to be accomplished. 



Woolman and Humphrey x have supposed that the failure of 

 chlamydospores to germinate in small closed vessels is due to the 

 lack of sufficient free oxygen ; but, in the experiment recorded 

 above where the stack of watch-glasses was kept under a bell- jar, 



1 H. M. Woolman and H. B. Humphrey, Studies in the Physiology and Control 

 of Bunt or Stinking Smut of Wheat, U.S. Department of Agriculture, Bull. No. 1239, 

 1924, p. 16. 



