Gcrndnation of Spores. 27 



from below to the surface of the soil, and possibly also the invisible hygro- 

 scopic moisture which the soil and vegetable matters absorb at night, especially 

 on nights when the fall of temperature is considerable — which causes the 

 great majority of the spores which are left m the ground to germinate. When 

 this happens, the absence of hosts (freshly germinated wheat-plants) to attach 

 themselves to and dry weather soon causes the young bunt-seedlings to 

 perish." It is probable that both methods occur in nature, and that while 

 the exposed spores are acted on by the sun's rays, those protected by the soil or 

 otherwise are induced to germinate by the moisture and perish in the absence 

 of a host -plant. 



Effect of Temperature on Germination. 



Eriksson found that the spores of some rusts germinated more freely after 

 being exposed to a temperature of 0° C, or even less, although an extremely 

 low temperature retarded germination. Schindler' experimented with 

 some smuts and found that with a dry heat the spores of Tilletia tritici could 

 stand 65° C. without losing their power of germination, but with a moist heat 

 of 45-50° C. they were rendered sterile. Cold, on the other hand, produced 

 but little effect, even after prolonged exposure to -20° C. 



******* 



In preparing slides of germinating spores for photographic purposes, the 

 water is first allowed to evaporate under cover, then absolute alcohol is added 

 as a fixing agent. This is gently moved to and fro for a few minutes, and after 

 drying, the stain is directly applied. The most generally useful stain is 

 Bismarck Brown, which gives a beautiful golden-brown tint to the promycelia 

 and conidia. Although it stains quickly the specimen may be left in it for 

 at least twenty minutes without injury. The excess of stain is next drained 

 off or washed off, and, if too deeply stained, it can be rendered lighter by the 

 application of dilute alcohol. The object is then mounted in glycerine and 

 water (half and half) in the usual way. 



