214, Illinois State Laboratory of Natural History. 
M. salicina, Lév. 
IZ., II. Amphigenous, the uredo mostly hypophyllous, and 
the teleutoform more often epiphyllous. Uredosori small, ‘cir- 
cular, often thickly spread over the leaf surface, surrounded by 
a thick row of paraphyses, which are strongly enlarged and 
rounded above; uredospores subglobose or elliptical, finely 
echinulate, 12-15 by 14-18 u; teleutosori various in size, usu- 
ally flat, irregular. often thickly associated or confluent, crust- 
like, becoming reddish brown or dark brown; teleutospores ob- 
long, in transverse section polygonal, about 10 by 30-37 zp. 
On leaves of Salir cordata: McHenry, Aug. 23, 1242, IL, 
Aug. 24, 1276 and 1271. 8S. longifolia: McHenry, Aug. 24, 
1254, IL, Aug. 31, 1396, IT., WL; Lake, Aug. 27,1350, IL, IIT.; 
Lee, Sept. 11, 5780, IT.; LaSalle, Sept. 14, 2500, IT., ITI.; Henry, 
Sept. 28, 1707, II. Salix sps.: McLean, July 18, 2498, IL, 
July 20, 2497, IT., Aug. 4, 2499, ID.; Piatt, Aug. 17, 1096, IL; 
McHenry, Aug. 24, 1278, IT., 1288, II.; Lake, Aug. 27, 1851, IT., 
IIL; Kane, Aug. 90, 1375, II., III,; LaSalle, Sept. 20, 1599, 
IL., JIL; Rock Island, Sept. 21, 1618, II.; Jersey, Oct. 14, 6315, 
IL, I.; Union, Oct. 24, 1977, IL.; Pulaski, Nov. 4, 2228, IL., 
TI. 
Thiimen thinks what is included in the above should be 
separated into the following species, for which he has given 
descriptions: M. Biglowii, M. capreanum, M. Hartigii, M. 
meduse, M. vitelline, (Hedwigia XVIII. [1879] p. 77, and Bul- 
letin Torrey Botanical Club, VI. p. 216). 
M. populina, Lév. 
IL, HI. Amphigenous. Uredosori small, scattered over 
the surfaces of the leaves, usually more numerous below, 
circular, surrounded by a dense row of paraphyses, which are 
clavate or strongly enlarged and rounded above, powdery, 
orange-yellow; uredospores varying from subglobose to oblong 
or clavate, echinulate, 18-20 by 21-80 u; teleutosori scattered, 
mostly thickly studding both surfaces of the leaf, flat, compact, 
crust-like, often confluent, reddish brown; teleutospores oblong, 
prismatic, epispore thin, smooth, one-celled, 15 by 36-45 u. 
On leaves of Populus tremuloides: McHenry, Aug. 20, 
1196. P. monilifera: Tazewell, July 22, 2509, II.; McLean, 
