CHAPTER XV 



MYRIANGIALES 



The Myriangiales, like the Perisporiales, lead directly from the 

 Plectascales, but their origin undoubtedly is more remote than that of 

 the Perisporiales, perhaps at the stage of the Gymnoascaceae. If one 

 imagines that the ascogenous hyphae of the Gymnoascaceae are longer 

 so that they penetrate the whole hyphal mat which becomes compacted 

 into a pseudoparenchymatous stroma, one has forms like primitive 

 Myriangiales. These form pulvinate, irregular stromata in whose inte- 

 rior the asci are irregularly arranged in one or more layers; the ascospores 

 are liberated only by the disintegration of the stromatal layers above 

 them. 



Fig. 136. — Kusanoopsis guianensis. Diagrammatic section through a leaf showing two 



stromata. (Stevens and Wecdon, 1923.) 



Thus the Myriangiales (like the Perisporiales) are angiocarpous but 

 at maturity every ascus lies embedded singly in the stromatal core, not 

 tufted. The ascus chambers or cavities are called loculi. 



As none of the forms have been studied cytologically, our morphologi- 

 cal discussions in regard to the Myriangiales still lack ontogenetic bases. 

 According to the differentiation of the stromata and the number of 

 ascogenous layers, they may be divided into a series of families, five of 

 which we will discuss here: the Myriangiaceae, Plectodiscellaceae, 

 Saccardiaceae, Dothioraceae and Pseudosphaeriaceae. Their mor- 

 phological relationships are given in the summary at the close of this 

 order. 



Myriangiaceae. — These are parasitic, more rarely saprophytic on 

 leaves, bark and insects. Their distribution is chiefly tropical or sub- 

 tropical. The consistency of their stromata is often suggestive of that of 

 the Hypocreales, although in Myriangiam itself they are more cartilagi- 

 nous-gelatinous and generally brittle. According to the formation of the 

 asci, they may be divided into two types. In one type, the asci are 

 scattered irregularly over the whole stroma. In the other type they are 



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