148 A Monograph of the Erysiphaceae 



a 



pendages with a much more closely and regularly branched apex 

 of J/! alni. 



The study of American examples oi M, alni, however, at once 

 shows us that we havelong-appcndaged forms certainly connected 

 with this species; it is impossible, e, g.^ in face of the numerous 

 intermediates, to regard the plant described as M, exclnsa Cooke 

 and Peck (a form with very long appendages) as anything but a 

 well-marked variety oi M. alni. 



More than this, there occurs in America a plant on Vaccinmm^ 

 etc., described as AL vaccinii^ but which must also be regarded as 

 variety of M, alni in which we occasionally find much the same 

 kind of apical branching as in the var. divaricata. It is even possi- 

 ble that it will eventually be found necessary to unite the American 

 variety vaccinii with the European var. divaricata. 



Considering these facts, we are forced to the conclusion that 

 in America, where the species is apparently more abundant than 

 in Europe, M. alni has varied and produced long-appendaged 

 varieties on several host plants, while in Europe only one very 

 similar variety has been produced on Rhauuiits Frangida. 



A further proof of the relationship of the present plant with M. 

 alni is afforded by the Japanese specimens of M, alni on Coryhis 

 rostrata, var. mandschiirica^ which frequently sho^v a loosel}^- 

 branched apex with spreading branches. 



Speshncw (338) records M. divaricata on Rliammis catJiartica 

 from Transcaucasia. As this plant is a common host for M. alni, 

 it will be best to wait for confirmation before accepting this record 

 of the occurrence of divaricata in Asia, on a new host-plant. 



Since the above remarks were written I have seen examples 

 one in the Herbarium of the British Museum (South Kensington), 

 and one in the Herbarium of the Florence Museum, of the speci- 

 men no. 142 (ii42)inthe Exsiccati " Erb. Critt. Ital. ser. i. 

 (Part of the latter specimen is now deposited in the Kew Her- 

 barium.) These specimens are labelled " Eiysiphc loniccrae," and 

 the host plant is Loniccra cacridea. The fungus, however, is not 

 the species named (which is described above, as M. alni, var. 

 lonicerac) but belongs to the present variety divaricata. 



These examples on Loniccra coerulca have long flaccid appenK^- 

 ages, 4-7 times the diameter of the perithecium, with often the 



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