74 



FUNGI. 



FIG. 40. 



dom are spores and threads colourless or of bright tints. In 

 the Mucedines, on the contrary, the threads are never coated, 

 seldom dingy, mostly white or of pure colours, and the spores 

 have less a tendency to extra development or multiplex septa- 

 tion. In some genera, as in Peronospora for instance,* a 

 secondary fruit is produced in the form of 

 resting spores from the mycelium; and 

 these generate zoospores as well as the 

 primary spores, similar to those common 

 in AlgcB. This latter genus is very de- 

 structive to growing plants, one species 

 being the chief agent in the potato disease, 

 and another no less destructive to crops of 

 onions. The vine disease is produced by a 

 species of Oidium, which is also classed 

 with Mucedines, but which is really the 

 conidiiferous form of Erysiphe. In other genera, the majority 

 of species are developed on decaying plants, so that, with the 

 exception of the two genera mentioned, the Hyphomycetes exert 

 a much less baneful influence on vegetation than the Conio- 

 mycetes. The last section, including the Sepedoniei, has been 

 already cited as remarkable for the suppression of the threads, 

 which are scarcely to be distinguished from the mycelium ; the 

 spores are profuse, nestling on the floccose mycelium; whilst 

 in the Trichodermacei, the spores are invested by the threads, as 

 if enclosed in a sort of false peridium. A summary of the 

 characters of the family may therefore be thus briefly ex- 

 pressed: 



Filamentous ; fertile threads naked, for the most part free or 

 loosely compacted, simple or branched, bearing the spores at their 

 apices, rarely more closely packed, so as to form a distinct common 

 stem = HYPHOMYCETES. 



Having thus disposed of the Sporifera, we must advert 



to the two families of Sporidiifera. As more closely related 



to the Hyphomycetes, the first of these to be noticed is the 



* De Bary, A., " Recherches sur les Champignons Parasites," in "Ann. des 



Sci. Nat." 4 rae se"r. xx. p. 5 ; " Grevillea," vol. i. p. 150. 



