NORTH .\mp:rican parasitic exoasce.t-:. 



93 



I shall classify the parasitic Kxoascea' according to the de- 

 cisions of Professor Sadebeck subsequent to his exhaustive 

 researches into their life-history, as set forth in his latest mon- 

 ograph (93). Prior to his publication in 1883, uniting all 

 forms in one genus. Jixotrsn/s. the\' were divided into the 

 three genera. Tafhri}ia Fries, Ascomyccs Mont, et Desm.. and 

 Exoascns Fuckel. It remains to be stated what these generic 

 distinctions were. 



According to Johanson ( "85 ). their union in one genus was 

 iidvisable, but he preferred apph ing to it the oldest name, 

 Taphrina Fries, which considering the rules of pi^iority gen- 

 <eralh' obser\ed in botanical nomenclature, it must be acknowl- 

 edged seemed the most fitting. 



Dr. B. L. Robinson ( "87 ) thought best to follow Johanson. 

 Rostrop ( "90 ) also, in his studies of Danish forms, makes use 

 of the same name, and other authors have done likewise 

 ( Fr S. '91)- But from the data of Professor Sadebeck and 

 his logical conclusions therefrom they must again be divided, 

 the basis of re-classitication being their comparative structure 

 and life-histories. The species whose asci arise from no uni- 

 versal hvmenium are to be separated generically from those 

 "whose asci arise onh' from an universal Ininenium. Those 

 Avhose asci develop singl\- from the terminal branches of the 

 mvcelium hctivccu the epidermal cells are to be united into a 

 new genus called Magiuniclla. In the genus Exoasciis are 

 placed all the species possessing a perennial mvcelium and 

 which cause a deformation of entire twigs. While in the 

 genus Taphrina will remain onlv those species which have no 

 perennial mycelium and cause only local affections. 



The old genus ^{icoiiiyccs is absorbed, there remaining no 

 logical grounds for its existence. It has been proven when 

 studied under Ascomyccs tosquiiictii West. (Magnus, "74) and 

 Ascomyccs cndogriitis Fisch. ( '85 ) that these are mycelial fungi, 

 the entire mvcelium being exhausted in the formation of the 

 ascogenous cells; and that what was figured by Magnus as an 

 epidermal cell from the interior of which he supposed the 

 ascus to spring, --each ascus being an individual plant," was 



