SPOROBOLOMYCES 189 



parent cell budded in the interval between the production of its 

 second and of its third spore. 



Sometimes a sterigma becomes branched, and yeast cells with 

 bifurcated sterigmata are shown in Fig. 89 (p. 181). The process 

 of branching was not observed. Presumably a spore is produced at 

 the tip of each sterigmatic branch, and it is therefore probable that 

 of the yeast cells shown in Fig. 89 the one with four sterigmatic 

 points produced four spores and the one with three sterigmatic 

 points produced three spores. Guilliermond, 1 in an illustration, 

 shows a cell of S. salmonicolor with two bifurcated sterigmata and 

 four spores, a spore being situated on each of the four sterigmatic 

 tips. It seems to me probable that the four spores were formed 

 not simultaneously but in succession and that they were all found 

 in situ by Guilliermond * because the unfavourable atmospheric 

 conditions of his culture prevented any of the spores being discharged 

 violently into the air. 



I have never seen two spores developing on either a single 

 sterigma or on two sterigmata of a yeast cell at one and the same time 

 and have no reason to suppose that such a simultaneous development 

 ever occurs in Sporobolomyces. We may therefore accept the view 

 that, in Sporobolomyces, whenever a cell produces several spores, the 

 spores are always produced in succession. 



Nuclear Phenomena. — It seemed possible that the behaviour of 

 the nuclei in the yeast cells when budding and producing spores 

 might throw some light on the taxonomic position of the genus 

 Sporobolomyces. On this account Miss Macrae and I, in 1927, 

 without any knowledge of Guilliermond 's observations and before 

 his paper appeared in January, 1928, undertook a cytological investi- 

 gation of S. roseus. An account of this investigation, the results of 

 which confirm those of Guilliermond, will now be recorded. 



Slides were dipped in malt -agar and placed in a Petri dish on a sheet 

 of moist filter-paper, and then the base of another Petri dish contain- 

 ing a colony of S. roseus growing on malt-agar was inverted over the 

 first Petri dish . After 1 5-20 minutes a sufficient number of spores had 

 been discharged and had fallen on to the agar slides. The inverted 

 base of the second Petri dish was then removed and replaced 

 1 A. Guilliermond, loc. cit., p. 251, Fig. 4. 



