THE RECEPTACLE 



39 



absent in a few genera. In one group only, the Zophiostomaceae, 

 the mouth is broad and compressed. The fructification there- 

 fore is always enclosed, as it is in the case of a peridium, but 

 this is their only point of agreement. "Whatever the form of 

 the carpophore, the perithecia are always crowded together on 

 the upper portion, and even when the carpophore is globose it 

 is flattened at the base, and as the perithecia approach the 

 base they are smaller, less numerous, and often imperfect. As 

 already stated, the perithecia are always peripherical, and in a 

 single series ; but if, in rare cases, there is a second series, the 

 necks of the perithecia are elongated so as to reach the surface 

 of the stroma. When a great number of perithecia are collected 

 together, and immersed in the matrix, a kind of stroma is formed 

 from the matrix, as in Eutypa ; but when on the surface, a 

 regular stroma is formed upon the mycelium, which is fleshy 

 in Mypocrea and carbonaceous in Hypoxylon, and the perithecia 

 are closely packed and immersed in the stroma, which is per- 

 forated by the ostiola. The densely 

 aggregated perithecia may sometimes 

 be fused together so as to resemble 

 ( an effused stroma. There are some 

 genera in which the perithecia seem 

 to be obsolete, or only formed from 

 the stroma, in which the perithecia 

 appear only as cells, as in Phyllachora ; 

 but the walls of the perithecia are 

 possibly fused with the stroma and 

 not wholly absent. The character of 

 the fructification may be entirely 

 different, while that of the perithecia 

 remains the same. The same peri- 

 thecium, to all external appearances, may belong either to 

 the Pyrenomycetes or the Sphaeropsideae. It may be a Diplodia 

 or a Plaeospora. 



It may be necessary to refer incidentally to a modification 

 which is almost intermediate between an excipulum and a peri- 

 thecium, which is prevalent in the comparatively small family, 

 the Hysteriaceae. Here the excipulum closes from two opposite 

 sides, leaving a slit down the centre. When well moistened 



Fia. 21. — Receptacle of sporo- 

 raega in Hysteriaceae, with 

 ascus. 



