CA PS ULA R FUNGI-P YRENOM YCE TES 



219 



Fig. 102. — Asci and sporidia of 

 Pleos2)ora. 



name suggests, are normally found growing on leaves, some- 

 times living and sometimes dead. The former are more or 

 less destructive parasites, and are found not only on the leaves 

 of trees and shrubs, but also on ^^ 

 herbaceous plants, and on the fronds 

 of Cryptogams. The perithecia are 

 immersed in the substance of the 

 leaf, sometimes scattered, but often 

 in groups. They are thin and 

 membranaceous, usually minute, and 

 perforate at the apex. When grow- 

 ing upon living leaves they are 

 mostly seated on discoloured spots, 

 caused probably by the delicate 

 mycelium destroying the vitality of 

 the cells. Similar blanched spots, 

 with analogous minute perithecia 

 seated upon them, are to be met 

 with in several genera of 8'phaeroj}- 

 sidcae, such as Phyllostida, Scpioria, 

 etc. ; but the asci are absent, and the minute sporules 

 are produced at the tips of slender sporophores. In certain 

 cases these are believed to be in some manner connected 

 with foliicolous Sphacriae, as a stylosporous or imperfect 

 condition, but how they are connected has not yet been 

 determined. Of the genera in this subfamily Laestaclia has 

 the sporidia continuous, or without septa ; in Sphaerclla they 

 are uniseptate, and are very numerous in species. In 

 Sphacrulina the sporidia are either three or many septate. 

 Under this genus are included the foliicolous species of the 

 genera Metasp)liaeria and Liptospliacria, so that in some the 

 sporidia are slightly coloured. In one other genus, that of 

 Linospora, the sporidia are very long and thread-like. 



The last subfamily is that of Microthyriaceae, and this is 

 somewhat of an outside group, as the perithecia are different in 

 form and structure, being superficial, or nearly so, either membran- 

 aceous or somewhat carbonaceous, dimidiate and flattened almost 

 like a shield, formed of radiating cells, and either pierced with a 

 pore in the centre or with out one. The genus Microthyrium seems 



