Uncinula 83 



septate at the base, hyaline and thin-walled throughout, usually 

 gradually and slightly enlarged upwards, apex simply uncinate or 

 occasionally more or less hclicoid ; asci 8-14, rarely only 4-6, 

 elliptic-oblong or broadly ovate, usually stalked, 5 5-80 x 30-40 /j', 

 averaging 68 x 36 fx; spores 4-6, 20-26 x 10-15 f^- 



Hosts.— Popiilm alba, P. angnstifolia (6), P. bahainifera and 

 var. candicans, P. cUiata, P. grandidcnlata, P. Jictcrophylla, P. 

 mojiilifera, P. nigra, P. pyramidalis, P. tramda, P. trcmidoidcs, P. 

 trichucarpa, Salix alba, S. angnstifolia (57), 5. aiirita, S. Capraca 

 and var. pendula, S. cinerea, S. cordata, S. daphnoidcs, S. discolor, S. 

 flavescc7is and var. Scoulcriana, S. fragilis (22) (344), 5. glaitca (6), 

 S. linmilis, S. incana (230), vS". livida, S. longifolia (6), 5. nigra 

 and var. falcata, S. nigricans, S. pctiolaris, S. purpiwca, S. pyrolac- 

 folia (347), 5. repens, S. scricca, S. Scringiana, S. triandra, 5 

 Urbaniana, S. vinunalis \_Bcinla alba (107) (176) (204) (214) 

 xh^l^ (394)) BnxHS scnipcrvircns {^^l 



Distribution. — Surope : Britain, France, Portugal, Belgium, 

 Netherlands {2(>3), Germany, Switzerland, Italy, Austria-Hungary^ 

 Denmark, Norway, Sweden, Finland, Russia. 



Asia: Transcaucasia {^^^^y Sibei'ia (Minussinsk), India, China 

 (Yunnan), Japan. 



North America : United States — Maine, Vermont, Massa- 

 chusetts, New York, New Jersey (53), Carolina (90), Ohio, Mich- 

 igan, Indiana, Illinois, Mississippi (361), Wisconsin, Missouri, 

 Iowa, Minnesota, Kansas, Dakota, Montana, Wyoming, Wash- 

 ington, California. Canada — -Ontario, Quebec, 



The most widely distributed and the most variable species of 

 the genus, but, as a rule, easily recognized by the numerous simple 

 appendages shghtly exceeding the diameter of the perithecium. 

 The appendages are usually slightly enlarged upwards (but not 

 sufficiently so as to make the apex club-shaped) and remain 

 hyaline and thin-walled throughout, not becoming thick-walled 

 or refractive towards the base, as is the case with several allied 

 species. 



Although there can be no doubt that the two forms growing 

 respectively on poplars and willows constitute but a single species, 

 we usually find these two forms characterized as follows. The form 

 of [/, salicts occurring on species of 5^//-rhas uniformly larger peri- 



