i 9 o RESEARCHES ON FUNGI 



by an ordinary Petri-dish cover. The spores soon germinated and 

 gave rise to small yeast colonies which were suitable for investigation. 



A slide bearing some colonies in the desired state of development 

 was immersed in formalin acetic alcohol * for about eight hours and 

 then, to remove the acetic acid and formalin, it was thoroughly 

 washed in several changes of 50 per cent, alcohol. The alcohol 

 was then removed by passing the slide through 35, 20, 15, 10 and 

 5 per cent, solutions of alcohol to pure water. 



The staining of the yeast cells was accomplished as follows. 

 The slides bearing the colonies growing on the agar film were placed 

 in a 4 per cent, solution of iron-alum for 20 hours, washed in running 

 water for an hour and a half, and transferred to • 5 per cent, aqueous 

 solution of haematoxylin. After lying in the haematoxylin for 20-24 

 hours, they were washed in running water for 10 minutes and then 

 placed in a Petri dish in a 2 per cent, solution of iron-alum where 

 they were watched under the microscope until the de-staining of 

 the colonies had progressed sufficiently far. The slides were then 

 washed in running water for an hour, after which they were placed 

 in an open Petri dish containing 10 per cent, glycerine. The dish 

 was covered by a sheet of filter-paper to protect it from dust. In 

 the course of three days, the water in the glycerine gradually 

 evaporated. As soon as evaporation was complete, the slides were 

 removed from the glycerine and the stained colonies were mounted 

 in Kayser's glycerine-jelly. 



In successfully made j)reparations the nuclei could be readily 

 observed as rounded bodies more deeply stained than the cytoplasm, 

 each of them possessing a nuclear membrane and a conspicuous 

 nucleolus. 



Each yeast cell contains only a single nucleus, as may be seen 

 in Fig. 95, A and B. When budding takes place, the young bud is 

 at first devoid of a nucleus (C, a). Then the nucleus of the parent 

 cell undergoes division and one of the daughter nuclei passes into 

 the bud, the other remaining in the parent cell (C, b-e). In the rare 

 instances in which a dividing nucleus was actually observed, the 

 division appeared to be taking place at the neck joining the parent 

 cell with its bud (C, b, c). 



1 Formalin 5 cc, acetic acid 5 cc, and alcohol 90 cc. of a 50 per cent, solution. 



