SPOROBOLOMYCES 197 



spore e bears a branched sterigma and the top of each branch is 

 crowned with a spore. The two younger spores and the parent 

 spore all contain, as usual, a single nucleus. It is probable that, 

 owing to abnormal culture conditions, one of the two younger spores 

 failed to be discharged as soon as it became mature, with the result 

 that it was left on the sterigma whilst the sterigma branched and 

 produced a second spore. From this discussion it seems probable 

 that the development of the abnormal morphological structures 

 illustrated in Fig. 99 was not accompanied by any abnormalities 

 in nuclear division. 



We may conclude from the various observations recorded in this 

 Section that the yeast cells and spores of Sporobolomyces roseus each 

 contain only a single nucleus, and that at no stage in the life-history 

 as observed up to the present do the nuclei ever come together to 

 form conjugate pairs or fuse with one another. 



The Taxonomic Position of Sporobolomyces.— The taxonomic 

 position of Sporobolomyces, as we have seen in the Introduction, 

 has been discussed : (1) by Kluyver and van Niel who suggested 

 that the genus belongs to the Basidiomycetes ; (2) by Lohwag who 

 opposed this view, and (3) by Guilliermond who asserted that 

 Sporobolomyces ought to be given a special place in the classifica- 

 tion of the fungi and that its affinities are as yet unknown. I am 

 of opinion that Sporobolomyces is of basidiomycetous origin for 

 reasons that will be adduced in what follows. 



The chief facts which must be taken into account in any attempt 

 to determine the origin and affinities of Sporobolomyces are the 

 following : 



(1) Sporobolomyces is yeast-like in form and in its mode of 

 vegetative multiplication. 



(2) Sporobolomyces produces conidia on sterigmata aerially. 



(3) The mode of development of a conidium on its sterigma and 

 the drop-excretion mode of discharge of the conidium in Sporo- 

 bolomyces are exactly similar to the mode of development of a 

 basidiospore on its sterigma and the drop-excretion mode of dis- 

 charge of the basidiospore in the Hymenomycetes, the Uredineae, 

 and Tilletia. 



(4) Sporobolomyces, as so far investigated, never possesses 



