98 NORTH AMERICAN FLORA [VoLuME 7 
Aecia erumpent, without peridia or paraphyses. Aeciospores globoid; wall colorless, 
finely verrucose. 
Uredinia erumpent, pulverulent, without peridium. Urediniospores borne singly on 
pedicels ; wall colorless, verrucose. Paraphyses intermixed with the spores, numerous, capi- 
tate, large and thick-walled; peripheral paraphyses usually thinner-walled and less capitate. 
Télia indehiscent, in waxy layers. Teliospores one-celled, closely compacted into a 
single layer, prismatic or ellipsoid; wall smooth, colored. 
Type species, Uvedo Helioscopiae Pers. (on Euphorbia Helioscopia). 
Urediniospores smooth on the thickened sides. 1. U. Medusae. 
Urediniospores without smooth spots. 
Urediniospores small. 
Walls thick, 2-34. 
Walls medium, 1.5-2.. 
Walls thin, 1-1.5 x. 
Urediniospores large. 
Walls thick, 2.5-3.54. 
Walls thin, 1.5-2e. 
Paraphyses clavate. 
Paraphyses capitate. 
1. Uredo Medusae (Thiim.) Arth. Résult. Sci. Congr. 
Bot. Vienne 338. 1906. 
Melampsora Medusae Thiim. Bull. Torrey Club 6: 216, 1878. 
O. Pycnia chiefly epiphyllous, scattered or somewhat gregarious, minute, punctiform, 
pale-yellow, inconspicuous, subcuticular, hemispherical, 40-80 in diameter, half as high. 
I. Aecia chiefly hypophyllous, scattered or somewhat gregarious, small, 0.1-0.3 mm. 
broad, round or oblong, pale-yellow fading to white, inconspicuous, formed between epidermis 
and mesophyl, soon naked, pulverulent, ruptured epidermis noticeable; aeciospores glo- 
boid, 17-22 by 17-24; wall colorless, thick, 2.5-3u4, minutely verrucose, with minute, 
crowded papillae, pores indistinct. 
ON PINACEAE: 
Larix sp. Proven by cultures, but not yet collected. 
. U. confluens. 
. U” alpina. 
U. Rostrupiana. 
. U”. Bigelowtt. 
. U. albertensis. 
U”. Lint. 
NA TH AWD 
Il. Uredinia amphigenous, or only hypophyllous, scattered, roundish, small, 0.2-0.4 
mm. across, early naked, somewhat pulverulent, orange-yellow, fading to pale brownish- 
yellow, ruptured epidermis usually inconspicuous; urediniospores ellipsoid or obovate- 
ellipsoid, 15-18 by 22-30, usually flattened laterally ; wall colorless, 2.5-3 4, or up to 104 
on the flattened sides, sparsely and evenly verrucose, with fine papillae, except on the flat- 
tened sides which are smooth; paraphyses numerous, intermixed with the spores, capitate, 
smooth, 40-65 long, head 14-25 broad, wall thick, 3-64, peripheral paraphyses thinner- 
walled and more clavate. 
[Il. Telia amphigenous, or only hypophyllous, scattered, or somewhat confluent, irreg- 
ularly roundish, small, 0.2-0.4mm. across, slightly elevated, light reddish-brown, becoming 
deep chocolate-brown, subepidermal ; teliospores prismatic, 12-15 by 30-454; wall smooth, 
cinnamon-brown, uniformly thin, 14. 
ON SALICACEAE : 
Populus angustifolia James, Montana, Wyoming. 
Populus balsamtfera 1,,, Montana. : 
Populus candicans Ait., lowa, Montana, Wisconsin. 
Populus deltoides Marsh. (P. angulata Ait., P. canadensis Moench, P. Medusae Benth., P. 
monilifera Ait., P. virginiana Dum.), Alabama, Illinois, Indiana, Iowa, Louisiana, 
Maine, Massachusetts, Mississippi, Missouri, New York, Ohio, South Carolina, Wis- 
consin, 
Populus dilatala Ait. (P. nigra tialica Duroi, P. pyramidalis Salisb., P. ttalica Moench), 
Pennsylvania. ; 
Populus grandidentata Michx., Alabama, Indiana, New York, Ohio, Wisconsin ; Nova Scotia. 
Populus occidentalis (Rydb.) Britton, lowa, Kansas, Nebraska, South Dakota. 
Populus tremuloides Michx., Indiana, Montana, Ohio, Vermont, Wisconsin. 
Populus trichocarpa T. & G., California, Idaho, Washington. 
Type LOCALITY: Aiken, South Carolina, on Populus angulata. 
DISTRIBUTION: Nearly throughout the United States, and northward. 
ExsiccaTr: Kellerm. Ohio Fungi 27, 45, 144, 145; Carleton, Ured. Am. 7, Griff. West Am. 
Fungi 369; Thiim. Myc. Univ. 1237; Ellis & Ev. Fungi Columb. 1067, 1068; Ellis, N. Am. Fungi 
1074, 10756, 1075c. 
