214 



COMPARATIVE MORPHOLOGY OF FUNGI 



the foot in Kusanoopsis, this second type spreads over the substrate in a 

 sterile stromatic plectenchyma, which, in the forms on animals, as M. 

 Duriaei maybe pulvinate, thestromatal hyphae being sclerotic and narrow 

 lumened (Fig. 137, C) ; those on plants, as in M . Pritzelianum, form only 

 a thin membrane of hyphae with unthickened walls. The cells on the 

 surface of the stroma become brown and change to a dark, otherwise 

 undifferentiated, rind. 



From this sterile basal stroma arises a tuft of numerous vertical 

 processes like a small pezizoid group (Fig. 137, A and B). They consist 

 of the same plectenchymatous ground tissue as the basal stroma. They 

 form the spherical asci in an apical, sharply defined, patelliform zone. 



nn r^r^TT^rj^^r^ 



Fig. 138. — Plectodiscella Pyri. 1. Section through fundament of a stroma. 2. Stroma 

 which has already ruptured the cuticle. 3. Section through a mature stroma. (1, 3 X 

 500; 2 X 82; after Woronikhin, 1914.) 



As in Kusanoopsis, these are arranged in several layers (except in the 

 Singhalese M. Thwaitesii) and contain hyaline dictyospores, liberated by 

 the crumbling of the peripheral stromatal layers. As this crumbling 

 proceeds more rapidly in the middle than at the edges, the mature 

 ascigerous parts seem more like an apothecium. Occasionally, when the 

 vertical portions are absent, the flat basal stromata form the asci in their 

 own apical portions (Petch, 1924). 



Myriangium forms only one branch of the Myriangiales and as such 

 ends blindly, hence the ontogenetic connections of the higher families 

 should be sought in the simpler Myriangiaceae, with undifferentiated 

 stromata similar to Kusanoopsis. From this point, development has 

 probably proceeded in two directions, one to the formation of special 

 coverings of the stromata, the other to the reduction of the number of 

 asci and their arrangement in a single layer. 



