PODOSPHAERA 33 



In Eriksson's own specimens (Fung. par. scand. exsicc. nr. 



233), liowever, the appendages measure i^ to 2^/( (averaging 2) 

 times the diameter of the perithecium. In the specimen in Rab.- 

 Wint. Fung. Eur. 3241 the appendages are sHghtly more unequal 

 in length, varying from 1-3 times the diameter of the perithecium. 

 As regards the number of the appendages, this is In Eriksson's 

 P. anaipariae 4-8, and in European specimens of P. niyrtillina, 



4-10. 



On the whole, P. ancupanac connects P. oxyacanthae with 



P. myrtillina, and cannot possibly be considered a separate 



species. 



It is, however, in dealing with American specimens that we see 



how completely "P. myrtillina'' merges Into P. oxyacanthae. 



The American plant is often erroneously called " P. tridactyla " 

 by American mycologists, or P. Kunzci (which includes P. tridac- 

 tyla) is quoted wholly as a synonym ; other authors, c. g., Earle 

 (no), have supposed that, the European P. myrtillina might be 

 something different from any of the American fonns. As a matter 

 of fact, were the species P. oxyacanthae and P. myrtillina to b 

 kept distinct most the American forms would fall under the latter, 

 althouo-h occurring on other hosts than Vaccininni, while P. 



b" '-"'^"""'a 



oxyacanthae would have to be confined to certain forms on Cra- 

 taegus, and to the form on Spiraea, which has been called P. 



minor E. C. How^e. 



A study of American examples on Crataegus, Prunns, Pyrus, 



Spiraea, etc., shows conclusively, however, that only a single 

 species exists, but one which is extremely variable in the length 

 and number of its appendages. Earle has some interesting re- 

 marks in his " Notes on the North American Forms of Podo- 

 sphaera" (no) on the subject of this variabihty, and this author's 

 conclusion that all the American forms must be included under the 

 single species P. oxyacanthae is undoubtedly correct. A specimen 

 in Professor Earle' s herbarium shows cleariy how completely the 

 long- and short-appendaged forms are connected. This specimen 

 is labeled "on Crataegus, Deland, lUinois, Sept., 1889. A. B. 

 Seymour." Many of the perithecia are identical in the few short 

 appendages with those of the European P. oxyacanthae on Cra- 

 taegus Oxyacantha ; other perithecia show, quite gradually, an in- 



