PYRENOMYCETES 297 



Dothidieae 



In this family the perithecia are always immersed in 

 a stroma. In the preceding families the perithecium has 

 always a distinctly differentiated wall of its own, quite dis- 

 tinct from the substance of the stroma in which it appears 

 as an independent structure inserted. In Dothidieae the 

 perithecium has no such differentiated, circumscribing 

 wall, hence the perithecia are sometimes called loculi or 

 cells. The fleshy and brightly coloured or clear-coloured 

 stroma separates Hypocreae from the present family. 



Many species are parasitic on living leaves, where they 

 form flattened or slightly convex patches of a shining 

 black, giving the leaf the appearance of having been 

 sprinkled with drops of pitch. 



Distribution general. 



Microthyrieae 



Distinguished by the minute, black, free, scattered peri- 

 thecia being remarkably flattened, and by the regularly 

 radiating arrangement of the pseudoparenchymatous tissue 

 of the perithecial wall. An ostiolum is present in some 

 species, and obsolete or apparently absent in others. 



Often growing as parasites on leaves, appearing under 

 the form of minute black dots. 



Widely distributed. 



Lophiostomeae 



The principal feature of the present family resides in the 

 structure of the ostiolum, which is distinctly elongated; it 

 is usually bounded by two parallel, thickish ridges, or lip- 

 like bodies, between which the true ostiolum or opening, 



