I7 6 RESEARCHES ON FUNGI 



many hours continuously, I have obtained clear evidence that one 

 and the same sterigma often produces not one spore only, but two 

 or three, or possibly four, spores in succession. My cytological 

 investigations, completed before Guilliermond's paper came to hand, 

 confirm his findings in respect to the nuclear condition of the yeast 

 cells and spores. An account of my own observations, which have 

 been carried through with the assistance of Miss Ruth Macrae, will 

 now be given. 



Cultures. — The species chosen for special investigation was 

 Sporobolomyces roseus. It was cultivated on 2*5 per cent, malt- 

 agar in Petri dishes, and in the course of a few weeks the colonies, 

 which are bright pink-red in colour, spread widely over the plates. 

 The yeast cells duly produced sterigmata and discharged numerous 



spores. 



New Petri-dish cultures were made from old ones, often by the 

 following method. The base of a Petri dish containing malt -agar 

 bearing a 8. roseus colony was inverted over the base of another 

 Petri dish containing sterilised malt-agar. The conidia discharged 

 from the sterigmata into the air fell downwards on to the agar in 

 the lower plate and thus sowed themselves on the new culture medium . 



Spore-deposits. — Spore-deposits can be collected readily from 

 colonies of Sporobolomyces species, as already known to previous 

 workers, by simply inverting a Petri dish in which a vigorous colony 

 is growing on malt-agar. The spores, on being discharged, then 

 fall on to the glass cover and there, in the course of a few days, 

 form a mirror-picture of the colony. An S-shaped colony of S. 

 roseus and its mirror-picture spore-deposit are shown in Figs. 84 

 and 85 respectively. A spore-deposit is white and the individual 

 spores in it are colourless. 



Method of Observing the Development and Discharge of the 

 Spores. — In Sporobolomyces, just as in the Hymenomycetes, the 

 Uredineae, and Tilletia, it is somewhat difficult to observe the 

 development and discharge of the spores, owing to the fact that it is 

 necessary to use the high power of the microscope and make con- 

 tinuous observations for some hours. If the yeast cells are kept 

 in a small closed chamber, the air soon becomes saturated with 

 water vapour, and then the spores are often not discharged in a 



