M. C. COOKE ON BLACK MOULDS. 261 



entirely cover the swollen tip, and form a round capital um. The 

 mass of threads do not form such a dense black stratum as is 

 common in Hebninthosporium, but only in sufficient number to cause 

 the affected portion of the thread to appear a little darker to the un- 

 aided eye. The stems and leaves of grass are less commonly 

 inhabited by a smaller species. The threads in all the species are 

 not unbranched, for in Sporocybe alternata they have alternate 

 branches, and in a smaller species, both found on paper and mill- 

 board, they are much branched in an irregular manner. The last 

 named is Sporocybe minima* which causes sooty patches on damp 

 paper, and has very small globose spores. 



Damp paper and millboard will also furnish another mould, which 

 would appear to the naked eye as the same ; but which will be found 

 on examination to offer a distinct mode of formation of the capitate 

 head. This is termed Stachybotrys atra. An examination of the 

 tips of the threads will show that they are there compounded of a 

 number of lobes, each of which is terminated by a spore. This is the 

 main distinction between the two genera. Perhaps, as a rule, the 

 spores are proportionately longer in Stachybotrys than Sporocybe. It 

 is somewhat curious that so many of the species in these-two genera 

 should be found growing on clamp paper. 



More rarely examples are to be found of a mould, with the spores 

 clustered together so as to form a distinct head, although by no means 

 a compact one, belonging to the genus Acrothecium. As far as I 

 am aware only two species have been found in this country, and those 

 very rarely. The threads are erect, stiff and unbranched, and the 

 large septate spores are arranged in a radiating manner about the 

 tips. In some respects it agrees with Helminthosporium, except that 

 the septate spores are aggregated at the tips of the threads. 



Here might be noticed a curious mould which hardly accords with 

 any of the artificial divisions adopted for the purposes of this 

 communication, in which the spores are compound, or formed of 

 three or four arms united at the centre in a triradiate manner. This 

 is Triposporium, a figure of which was given in the preceding com- 

 munication published in the Journal of the Club. The genus 

 Camptoum must also be included here. 



It was doubtless an error to include amongst the Dematiei the 

 genus CEdocephalum, which was so placed in the Handbook, on 

 authority of previous authors. At that time I had seen no speci- 



* Grevillea, vol. v., pp. 



