M. C. COOKE ON BLACK MOULDS. 255 



appear to be rough, nor are there such wide divergences in the mag- 

 nitude of the spores as in Heterosporium. Undoubtedly, as far as 

 the limits of species are concerned, the whole genus is in utter con- 

 fusion, and there is good work for some one to investigate all the 

 supposed species of Cladosporium, and embody the results in a mono- 

 graph. Perhaps in the production of the Handbook, the error was 

 rather in too great a reduction of the number of species. 



One species of Cladosporium, with its variety, which were included 

 in the Handbook under the name of Cladospoi ium dendriticum, I 

 am now disposed to follow the example of continental authors, and 

 recognise as the type of a genus as Fusicludium. Nearly all con- 

 tinental Botanists accept this genus, and I do not see that any good 

 purpose is served by remaining singular, with no other reason than 

 that of eccentricity. The features relied upon chiefly are the simple 

 spores, which never become septate, and the reduced threads. This 

 will form the third genus in the group with collapsible threads and 

 spores. The fourth has been accepted since the publication of the 

 Handbook.* 



Cercospora certainly is allied to the foregoing three genera, but dif- 

 fers very widely in the character of the fruit. It is a comparatively new 

 genus, and its species have been multiplied right and left until the 

 distinctions have become so refined that it is very difficult to discover 

 them. In fact, I very much doubt if the whole of the twenty or 

 thirty species could not well be comprised within some three or four 

 species. Many of these moulds are parasitic on the leaves of living 

 plants, occurring on spots which have been damaged, or on leaves 

 which have begun to fade. The mould is very minute and delicate, 

 the threads very short, being reduced to one or two cells, but the 

 spores are very long, slender, and thread-like, either containing a 

 row of nuclei, or divided by septa into numerous cells. Only one or 

 two of the supposed species have yet been found in Britain, of which 

 Cercospora reseda was detected by myself in Jersey. Many others 

 probably occur in this country. 



Any one who has examined with care a specimen of one of 

 the common species, or varieties, of Cladosporium, will not 

 fail to have noticed certain peculiar bodies mixed up with the 

 threads which appear to have no decided relationship with them. 

 These bodies are of the form of spores, more or less irregular 



* It is difficult to see in ScoMcotrichum any other than a mixture of 

 species of Cladosporium and I'usicladdum. 



