ON POPLAR 349 
solitary and epiphyllous, up to 1 mm. wide, at first covered by 
the raised epidermis and a layer of hyphe, at length uncovered 
and surrounded by the same, distributed over the whole leaf- 
surface ; spores distinctly oblong, 30—40 x 13—17 pw; epispore 
about 2 « thick, at the equator thickened up to 5—6 yu, covered 
with rather distant spines except at the summit which is 
smooth; paraphyses clavate-capitate, 40—70 x 14—18 wv, strongly 
thickened (up to 10 u) above. 
Teleutospores. Sori epiphyllous, minute but united in 
groups and confluent, distributed over nearly the whole leaf, 
covered by the epidermis, clear translucent-brown, then red- 
brown, and at length black; spores prismatic, rounded above 
and less so below, 40—50 or more x 7—10y; epispore pale, 
scarcely 1 thick, but reaching 24—3y above where it is 
faintly coloured and without evident germ-pore. 
Cxomata on Laria europaea; uredo- and teleutospores on 
Populus balsamifera (ontariensis), P. canadensis, P. nigra, P. 
pyramidalis (atalica), and also on other species, in September 
and October. Not uncommon. (Fig. 261.) 
The description of the czeomata is after Klebahn. This species is 
distinguished from M. Allii-populina by the following points: the elon- 
gated uredospores have a distinct equatorial thickening or rather swelling ; 
the teleuto-sori are epiphyllous, and the spores are very slightly thickened 
at the summit. On P. ontariensis I have seen the teleuto-sori so thick 
and crisp as to remind one of Phyllachora Ulmi on elm-leaves. 
11. Melampsora Tremule Tul. 
Melampsora Tremulae Tul. Ann. Sci. Nat. 1854, p. 95. Cooke, Handb. 
p. 522; Micr. Fung. p. 219. Plowr. Ured. p. 240. Sacc. Syll. 
vii. 589. 
(1) Me tampesora LaRIcI-TREMULAE Kleb. 
Caeoma Laricis Plowr. Ured. p. 262 p.p. 
Melampsora Larici-tremulae Kleb. in Forstlich.-naturwiss. Zeitschr. 
1897, p. 468. Fischer, Ured. Schweiz, p. 498, f. 315. 
4cidiospores. Ceomata solitary or in little groups, on 
yellowish spots, minute, scarcely 1 mm. diam., pale-orange or 
flesh-colour ; spores roundish, oval or polygonal, 14—17 x 12— 
16 «4; epispore about 1 » thick, verruculose, 
