22 



RESEARCHES ON FUNGI 



fuse with one another and that they grow together without any- 

 inhibitory effects being observable. 



In 1932, in a paper on Hyphal Fusions in Dermatophytes, 

 Davidson, Dowding, and Buller * recognised that hyphal fusions are 

 an important character of the mycelium of fungi which parasitise 

 the human skin, and they came to the following conclusions. In 

 Microsporon audouini, 2 M. lanosum, 3 and Trichophyton gypseum 4 

 hyphal fusions : (1) are formed between hyphae of one and the 

 same mycelium isolated from a single patient, (2) are formed between 

 any two mycelia of the same species isolated from two different 



patients, and (3) are not formed 

 between a mycelium of one 

 species and a mycelium of 

 another species (c/. Fig. 10). 

 The occurrence or non-occur- 

 rence of hyphal fusions between 

 hyphae of two mycelia of 

 different origin may be applied 

 as a criterion for identifying 

 species of dermatophytic fungi 

 whose specific nature is un- 

 certain. 



i 



Fig. 11. — Fusions between sporidia of two 

 different species of Ustilago : U. 

 longissima var. macrospora, sporidia 

 elongated, with U. bromivora, spori- 

 dia oval or lemon-shaped ; a, b, and 

 c, different sexual combinations. 

 From Kniep's Uber Artkreuzungen 

 bei Brandpilzen. 



1 he problem whether or not 

 two different allied species of fungi can fuse with one another, 

 either sexually or vegetatively, is of considerable interest from 

 the point of view both of genetics and of evolution. 



Sexual fusions must take place where hybrids are formed. 

 Naturally occurring hybrid fungi are at present unknown, but 

 certain hybrids have been obtained in artificial cultures. Thus 

 Saito and Naganiski 5 obtained zygospores in crosses between 



1 A. M. Davidson, Eleanor S. Dowding, and A. H. R. Buller, " Hyphal Fusions 

 in Dermatophytes," Canadian Journal of Research, Vol. VI, 1932, pp. 1-20, 22 Text- 

 figs, and Plates I— III. 



2 The commonest cause of ringworm of the scalp at Winnipeg. 



3 The cause of crusted lesions on the scalp and of circular red scaly lesions on the 

 glabrous skin. 



4 It attacks hairs in the beard area and causes sycosis parasitaria (tinea barbae). 



5 K. Saito and J. Naganiski, " Bemerkungen zur Kreuzung zwischen verschie- 

 denen Mucor-arten," Bot. Mag. Tokio, Vol. XXIX, 1915, pp. 149-154. Burgeff (next 



