Puccinia arnicalis Peck 1881

Puccinia arnicalis Peck, Bot. Gaz. 6: 227. 1881
Dicaeoma arnicale Kuntze, Rev. Gen. 3^: 467. 1898.
Uredinia amphigenous, chiefiy epiphyllous, scattered or gregarious, sometimes confluent, round or oval, 0.2-0.5 mm. across, early naked, cinnamon-brown, ruptured epidermis conspicuous; urediniospores globoid or ellipsoid, flattened laterally, when viewed with pores in faceview, 20-26 by 26-32 fx, when pores in side-view, 16-18 by 26-32 m; wall Ught chestnutbrown, moderately thick, 1.5-2 fx, very minutely and closely echinulate, appearing nearly smooth when wet, the pores 2, opposite and considerably superequatorial.
TeUa at first epiphyllous, becoming amphigenous, in open and irregular groups 2-5 mm. across, or extending for considerable distances along petioles or midribs, often scattered, round, 0.4-0.8 mm. in diameter, early naked, becoming pulverulent, chestnut-brown, ruptured epidermis inconspicuous; teliospores ellipsoid or obovate-ellipsoid, 18-26 by 28-38 m» rounded above, rounded or narrowed below, slightly or not constricted at septum; wall light chestnut-brown, uniformly thin, 1-2 /x, minutely and closely verrucose, the pore of upper cell often depressed half way to septum, the pore of lower cell usually about half way between septum and pedicel; pedicel colorless, very short, deciduous.
On Carduaceae:
Arnica cordifolia Hook., Colorado, Oregon, Utah. Arnica diversifoUa Greene (^1. latifoUa viscidula A. Gray), California, Oregon. Arnica latifolia Bong., Montana. Arnica pedunculata Rydb., Utah. Arnica rhizomata A. Nelson, Utah. Arnica suhplumosa Greene, Colorado, Type locality: Colorado, on Arnica cordifoUa.
Distribution : Mountains of Colorado to central California, and northward to northwestern Montana and Oregon.