POLYSTOMELLACEAE 



95 



radiate in the two largest families and marginally so in most genera of the third, 

 serves as a definite mark of recognition. 



The opposing views are probably to be reconciled by the assumption that the 

 order has arisen from Perisporiales through the Trichothyriaceae and has under- 

 gone fairly rapid and direct evolution into the discomycetc type, as indicated by 

 Hoehnel's reference of several genera to the Phacidiaceae. This development v^ras 

 more or less parallel to the much more extensive evolution of the sphaerial type, 

 which in the main line of descent is supposed to have led through the Hysteriaceae 

 to the Phacidiaceae also. As a consequence, the latter are regarded as diphyletic 

 at least, and the Discomycetes necessarily so likewise. The order is overwhelmingly 

 tropical in distribution, and its peculiar morphology and evolution are probably to 

 be ascribed to this fact. 



Key to Families 



A. Scutellum radiate 



1. Apothecia or hypostroma innate or erumpent 



2. Apothecia superficial, hypostroma none 



B. Scutellum radiate only at margin or not at all 



Polystomellaceae p. 95 

 Microthyriaceae p. 98 

 Micropeltaceae p. 100 



Though differences in insertion are not regarded as family criteria, the separation 

 of the first two families is more or less warranted by the fact that the majority of 

 the Polystomellaceae possess a hypostroma. The original l>"nits of this family, as 

 drawn by Theissen and Sydow in their monograph on the Dothideales (Ann. Myc. 

 13: 158, 1915), appear much more natural, and the Stigmateaceae and appended 

 genera of their latter treatment have been included in it (Ann. Myc. 15: 399, 403, 

 1917). Moreover, their family Trichopeltaceae, characterized by a membranous 

 mycelium or subiculum, has been merged in the Microthyriaceae. They have fol- 

 lowed Theissen in terming the order, Hemisphaeriales, and the third family, Hemi- 

 sphaeriaceae, but these names have been replaced in accordance with the sound 

 principle that the designations of families and orders should be based upon a repre- 

 sentative genus. 



Family 34. POLYSTOMELLACEAE 



22:514, 24:393; TS 13:158, 15:399 



Ascoma covered, erumpent, or typically superficial with an innate hypostroma, 

 dimidiate with radiate scutellum, round to more or less elongate; hymenium round 

 or linear, single or several and then concave and more or less locule-like, arranged 

 radially, circularly or irregularly; asci usually many in each hymenium, mostly basal, 

 parallel and clavate; paraphyses present or lacking. 



A. Ascoma subcuticular, persistently covered or 

 finally erumpent; paraphyses present 

 1. Ascoma persistently covered 

 a. Scutellum with a single hymenium beneath 



(1) Spores 1-celled 



(a) Spores hyaline 



(b) Spores dark 



(2) Spores 2-celled 

 (a) Spores hyaline 



X. Ascoma round 

 y. Ascoma elongate 



(x) Ascoma lichenicole 



(y) Ascoma not lichenicole 



Subfamily. Stigmateae 



Parastigmatea 

 Entopeltis 24:394, TS 401 



Diplocarpum 24:911 



Lichenopeltella 

 Leptopeltis 24:394, TS 401 



