i 7 8 RESEARCHES ON FUNGI 



yeast cells, and some of them fell on unoccupied agar at the periphery 

 of the yeast colony and there budded and initiated the formation 

 of new colonies. These new small colonies, which soon began to 

 produce sterigmata and spores on their own account, proved very 

 suitable for observation. The Petri-dish cover was removed and 

 replaced by a glass plate which had been cut across into two un- 

 equal parts (Fig. 86, c c). The two pieces of the glass plate were 

 placed over the culture-dish right and left of the yeast colony which 

 was to be observed with the microscope. Then the yeast colony 

 was brought into focus with the high power of the microscope, 

 whereupon most of the gap between the two pieces of glass plate 

 was covered over with a third piece of glass (Fig. 86, d). At intervals 

 between observations, the objective of the microscope was raised 

 and the two pieces of the plate were pushed together so as to com- 

 pletely cover the culture-dish. The temperature of the laboratory 

 was usually about 24° C. With the apparatus arranged as just 

 described, the development of certain yeast cells was successfully 

 watched for 10 or more hours (in one instance for 24 hours) before 

 it became appreciably abnormal. 



Observations on the Development of Sporobolomyces Colonies. — 

 In Fig. 87, a, is shown a spore which had been shot away from its 

 sterigma and had settled at a distance from the parent cell on the 

 surrounding malt -agar of the same plate. Stages in its germination 

 and in the production of a colony of 13 yeast cells in the course of 

 22 hours are shown from b to m in the same Figure. It will be 

 observed that the spore produced two buds, one from each end, 

 and that these daughter buds budded in their turn. In the last 

 stage shown, drawn 22 hours after the first stage, it will be seen 

 that three of the yeast -cells are producing sterigmata. These 

 sterigmata, doubtless, produced and discharged spores in the course 

 of the next two hours ; but, in this particular case, spore-formation 

 was not followed. The appearance of a spore on one of the sterig- 

 mata, as it might have appeared in side view, is indicated semi- 

 diagrammatically in Fig. 87 at n. 



Spores behave somewhat differently according to whether they 

 are sown on (1) a fresh medium or (2) an old medium. 



(1) When a spore germinates on agar in a new plate, it and its 



