THE SPORE AND ITS DISSEMINATION, 135 
posed, in which the sporidium (as in Perisporium vulgare) 
consists of four coloured ovate joints, which ultimately separate. 
Multiseptate fenestrate sporidia are not uncommon in Oueurbi- 
Fic. 75.—Spovidia of Fig. 76.—Spori- 
Valsa taleola. x 400. dium of Sporormia 
intermedia, 
taria and Pleospora, as wellas in Valsa fenestrata and some other 
species. In the North American Spheria putaminum the sporidia 
are extraordinarily large. 
The dissemination of the sporidia 
may, from identity of structure in the 
perithecium, be deemed to follow alike 
method in all. When mature, they are 
in a great measure expelled from the 
mouth of the perithecia, as is evident 
in species with large dark sporidia, 
such as exist in the genera Hypoxylon, 
Melanconis, and Massaria. In these 
genera the sporidia, on maturity, may 
be observed blackening the matrix 
round the mouths of the perithecia. 
Fic. 78.—Sporidium of Spheria 
putaninum. x 400. 
As moisture has an evident effect in producing an expul- 
