MYRIANGIALES 



223 



Unfortunately the species of Leptosphaeria, as all other Myriangiales, 

 have been only incompletely investigated ontogenetically. Only for L. 

 Lemaneae, on the fresh water red alga Lemanea, has Brierley (1913) 

 observed that, as in Pleospora and Penicillium " crustaceum," at the for- 

 mation of the perithecia, two hyphal branches embrace each other and 

 come into open communication at the tips; it seems, however, that 

 copulation may also occur without this helix formation between two 

 extended hyphal branches. Many species of Leptosphaeria are important 

 as causes of plant disease. The L. avenaria group, on numerous species 

 of grasses, are related to each other but differ in their conidial dimensions 

 and biologically according to their choice of host; their imperfect forms 

 belong to Septoria (Weber, 1922, 1923). Septoria secalis, for example, is 

 specialized on Secale cereale, S. Passerinii on Hordeum sp., S. Agropyri 

 on Agropyron repens, S. Bromi on Bromus inermis, Leptosphaeria avenaria 

 on Avena. Two other species have somewhat less specialized hosts, 

 as Septoria tritici and S. nodorum which both infect Secale cereale, Triticum 

 sp. and Poa pratensis. 



Summary. — The special distinction of the Myriangiales is that 

 every author circumscribes and divides them differently; they are an 

 order of transitional forms showing connections in all directions, but 

 the further we go into their ontogeny the more they seem to be the key 

 group to the higher Ascomycetes. 



As far as an interpretation may be based on the morphological 

 relationships of mature fructifications, there are presented in the following 

 diagram the relationships between the individual Myriangeles as the 

 author conceives them; it is obvious here, as in all diagrams of this type, 

 that we deal with types, not genera or species. 



The Myriangiales form the starting point with a massive, homo- 

 geneous, often highly colored stroma, in which the spherical asci lie 



MYRIANGIALES 



PLECTODISCELLACEAE 

 Plectodiscella 



DOTHIORACEAE 

 Parodiellina Chevalieropsis Botryosphaeria 



Bagnisiopsis 



Dothiora 



BagnTsiella 



PSEUDOSPHAERIACEAE 

 Leptosphaeria Didymella 



Pleospora 

 Pyrenophora 



SACCARDIACEAE 



Anhellia 



Sacoardia 



Eurytheca 



MYRIANGIACEAE 



rMyriangium 



Kusanoopsis" 



PLECTASCALES 



Diagram XXII. 



