340 Transactions British Mycological Society. 



in their examination of Ustilago antherarum Fr. They found 

 neither a fusion of two nuclei in the spores nor the migration 

 of one cell nucleus into the other cell during the anastomotic 

 union between the two sporidia. 



In 1915 Wilson (1915) published a short account of his work 

 upon the cytology of Tuhercinia primulicola. He found the cells 

 of the mycelium to be uni-nucleate, as are also the conidia 

 which arise from it. The conidia conjugate in pairs and the 

 nucleus of one passes through the connecting bridge into the 

 other, giving rise to a bi-nucleate structure. The chlamydo- 

 spores are formed in coils of hyphae which are bi-nucleate and 

 which have most probably developed from the fusion-product 

 of the two conjugating conidia. The spores are at first bi-nucle- 

 ate but subsequently the two nuclei fuse and the mature spore 

 is uni-nucleate. 



Paravicini (1917) published an important contribution to the 

 subject. He investigated the seven species into which the col- 

 lective species Ustilago Carho has now been divided as well as a 

 number of other species including Tilletia Tritici (Bjerk.) Wint., 

 Entyloma Calendulae (Oud.) de Bary, Urocystis Anemones (Pers.) 

 Wint., and Urocystis Violae (Sow.) Fisch. v. Wald. In all cases 

 he found the promycelial cells and the conidia to be uni-nucleate. 

 Where the conidia conjugate with one another there is a passage 

 of the nucleus from one spore to the other so that a bi-nucleate 

 conidium results. In those cases, such as U. Tritici and U. nuda, 

 in which no conidia are formed, the cells of the mycelium con- 

 jugate \\ith one another and bi-nucleate cells are established by 

 the migration of the nucleus from one cell to the other. The 

 spores are bi-nucleate and the two nuclei fuse so that the mature 

 spore is uni-nucleate. 



No work has hitherto been done upon the cytology of the 

 genus Melanotaenium. In the case of M. Lamii it was found to 

 be a matter of considerable difficulty to ascertain the number 

 of nuclei in the cells of the hyphae. These hyphae are usually 

 exceedingly fine and their walls, especially the septa, stain very 

 faintly with the dyes used. In the few favourable cases in which 

 both the hyphal walls and the nuclei were satisfactorily stained 

 two nuclei were present in each cell and it is most probable that 

 this is the constant number in the cells of these hyphae (fig. 8). 



The young haustoria are filled with dense cytoplasm and con- 

 tain two nuclei in each of the terminal branchlets, one lying in 

 each fork of the branchlet. It was not possible to determine 

 whether the branchlet is cut off from the main branch by a 

 septum, but if this should prove to be the case we have here 

 the bi-nucleate condition of the cells maintained in the haus- 

 torial apparatus. 



