378 RESEARCHES ON FUNGI 



more spores may be developed on the end of it in succession. When two 

 sterigmata are produced, each sterigma gives rise to at least one spore, 

 and one of the sterigmata (possibly both) may give rise to two spores in 

 succession. When three sterigmata are produced, each sterigma gives 

 rise to at least one spore. 



A yeast cell of Sporobolomyces roseus, between the production of two 

 successive spores, may bud off one or two daughter yeast cells. 



Sometimes a sterigma of Sporobolomyces roseus becomes branched and 

 then, presumably, a spore is produced on each branch. 



In Sporobolomyces roseus, whenever a yeast cell produces several 

 spores, the spores are developed not simultaneously but in succession. 



In Sporobolomyces roseus, the yeast cells and the spores which the 

 yeast cells develop on their sterigmata each contain a single nucleus and, 

 up to the present, no stage in the life-history of S. roseus has been observed 

 in which two nuclei come together to form a conjugate pair or in which 

 two nuclei fuse with one another. It is possible that S. roseus is hetero- 

 thallic, that so far it has been grown only in the haploid condition, and 

 that the mating of (+) and ( — ) strains might result in a sexual reaction. 

 It is also possible that S. roseus has lost all traces of sexuality. 



From the point of view of phylogeny, the most important characteris- 

 tics of Sporobolomyces are : (1) the peculiar shape of the conidium 

 which is due to its possessing an excretory hilum that is developed on one 

 side of the top of the sterigma, (2) the presence of a sterigma of typical 

 conical shape beneath each conidium, and (3) the discharge of the 

 conidium by the drop-excretion mechanism. 



The possession of the characteristics just enumerated, which are 

 identical with those concerned with the production and liberation of 

 individual basidiospores in all Hymenomycetes and Uredineae, clearly 

 indicates that Sporobolomyces belongs to the Basidiomycetes. 



The behaviour of the nuclei in Sporobolomyces, as ascertained up to 

 the present, cannot be used as an argument either for supporting or for 

 rejecting the conclusion that Sporobolomyces belongs to the Basidio- 

 mycetes. 



Chapter II. — The germination of a chlamydospore of Tilletia tritici 

 on culture media, the formation of the promycelium, the development of 

 the so-called primary and secondary conidia, and the development of 

 a saprophytic mycelium have been redescribed and illustrated. 



Six variations in the development of the primary and secondary 

 conidia of Tilletia tritici have been recorded and discussed. 



The germination of the chlamydospores of Tilletia tritici is dependent, 

 in a high degree, on the proper ventilation of the air above the substratum 

 upon which they are sown. Among the factors involved in ventilation 

 are the movement of the air and the prevention of saturation of the air 

 with water-vapour. The non-germination or delayed germination of 

 chlamydospores in small closed chambers is not due to insufficient oxygen. 



