250 



RESEARCHES ON FUNGI 



Fig. 122. — Tilletia tritici. A white 

 basidiospore-deposit on a dry 

 copper-sulphated glass slide, 

 formed in three days underneath 

 an inverted malt-agar-slope test- 

 tube culture like that shown in 

 Fig. 121, photographed against 

 a black background. The 

 spores fell through comparatively 

 moist air. Natural size. 



possibility of obtaining spore-deposits of this fungus, resembling 

 those of Hymenomycetes, at once presented itself. Accordingly, 



some Petri-dish cultures were in- 

 verted so that the basidiospores fell 

 on to the Petri-dish covers. After 

 24 hours inversion of a dish, the 

 spore-deposit was visible to the 

 naked eye as a thin white film. 

 Subsequently, spore-deposits were 

 collected by inverting agar cultures 

 over microscope slides. 



When a spore-deposit made on 

 the cover of a closed inverted Petri 

 dish during a period of 6-12 hours 

 is examined microscopically, it is 

 found to consist of thousands of 

 sickle-shaped basidiospores all of 

 which, except those most recently 

 discharged, have germinated on 

 the film of moisture on the surface of the glass. In fact, under 

 these conditions, it is impossible to obtain a spore-deposit in which 

 some of the spores have not 

 germinated. 



In order to obtain an 

 ungerminated spore-deposit 

 suitable for photomicro- 

 graphing and for making 

 measurements of spores, it 

 was found necessary to pre- 

 vent the spores from germin- 

 ating by allowing them to 

 fall on to a slide or Petri-dish 

 cover which had been treated 

 with a dilute solution of 

 copper sulphate or some 



other toxic substance. Usually, a few drops of the copper sulphate 

 solution were put on a slide, were spread over it with a glass rod, 



Fig. 123. — Tilletia tritici. A white basidio- 

 spore-deposit obtained by inverting a 

 vigorous, Petri-dish, potato-dextrose- 

 agar culture over a dry copper-sulphated 

 glass slide for several days. The copper 

 sulphate prevented the spores from 

 germinating. Photographed against a 

 black background. Natural size. 



