258 M. C. COOKE ON BLACK MOULDS. 



way. Mycologists need not be informed that Helicoma and 

 Helicocoryne are two genera constructed by Corda,* that Helico- 

 sporium and Helicotrichnm were two genera for which Neesf is 

 responsible, and that Helicomyces is accorded to Link.| These five 

 genera have all Helicoid spores, that is, elongated spores which are 

 coiled round like the spire of a snail shell. In order to avoid con- 

 fusion, it is well to fix some definite character to each of these 

 genera. Undoubtedly Helicotrichnm is essentially the same as 

 Helicosporium, and Helicocoryne is so much like Helicoma, that I 

 fail to detect any difference. We have thus reduced the genera to 

 three, but as Helicomyces has no threads, and consists only of 

 spores, which are parasitic on other moulds, it does not belong to 

 our subject, but, on the contrary, to the Torulacei. In the " Hand- 

 book" this genus should occupy the place of Helicosporium, which 

 was erroneously inserted in Torulacei, instead of Dematiei. The 

 two genera now left for illustration are Helicoma and Helicosporivm. 

 In Helicoma the spores are irregular in thickness, being attenuated 

 at the base usually, but always coarser than in Helicosporium, 

 distinctly multiseptate, mostly lateral ; and the threads are much 

 more robust. In Helicosporium the flocci are delicate, but rigid, 

 and the spores filiform, of equal length throughout, and generally 

 terminal, with indistinct septa. As far as hitherto ascertained two 

 species of each genus are British, i.e., Helicoma Mulleri, Ca., with 

 Helicoma viride (under Helicocoryne in the Handbook), and the 

 two species of Helicosporium, long since recorded. 



Externally, there is no feature by which these genera could be 

 distinguished from other of the black moulds. They form dirty, 

 greenish, or blackish patches on wood and bark, and are as much 

 like a Torula or Helminthosporium, as anything else, except perhaps 

 that the stratum is thinner, and not so decided. Helicotrichnm is, 

 undoubtedly rare, not only in Britain, but also on the Continent. 

 Of the two species, Helicosporium vegetum is the most delicate, with 

 very slender, simple threads, and small hyaline spores, whereas, in 

 Helicosporium pulvinatum, or what seems to me to be that species — 



* Helicoma, Corda (1837), Icon., i., p. 15. 



Helicocoryne, Corda (1854), Icon., vi., p. 9. 

 f Helicosporium, Nees (1816), Syst., p. (i8. 



Helicotrichnm, Nees (1818), Nova. Act. Leop., ix., p. 246. 

 % Helicomyces, Link. (1809), lierl. Mag., iii., p. 21. 



Helicotrichnm, Nees = Hcdicosporium , Ntes. 



Helicocoryne, Corda = Helicoma, Corda. 



