In the course of a general investigation of the fungi living in extreme environments new information was obtained on Herpotrichia nigra Hartig.2 This fungus is commonly referred to as brown felt blight or snow mold. The following observations are presented as contributions to our knowledge of the ecological life cycle of the fungus. Hartig (1888a), in his original description of H. nigra, called it a parasite of Picea excelsa, Pinus montana, Juniperus communis and Juniperus nana. In a subsequent paper (1888b) Hartig compared H. nigra with Trichosphaeria parasitica, a parasite of silver fir. Weir (1915) extended the host range of the brown felt blight to include the New World spruces and firs. Hedgcock (1932) also listed spruces, firs and junipers as hosts, and restricted infection of Pinus to the related species, Neopeckia coulteri (Peck) Sacc. Gaumann et al. (1934) on the other hand, were able to grow H. nigra on a malt agar medium and succeeded in causing infection of certain species of Pinus under laboratory conditions. Later (1943), H. nigra was reported from Colorado by Shope as a parasite of all species of conifers at higher elevations. Sturgis (1913) and Savulescu and Rayss (1928) compared the morphology of H. nigra with that of N. coulteri. Mytilidion fusisporium (Cooke) Sacc. was noted by Seaver (1915) as a fungus often growing in association with H. nigra. Weir (1915) reported seeing forests in the Pacific Northwest so badly infected with Herpotrichia that the trees appeared ragged. Evidently the fungus can be a serious pest of spruce seedlings being grown in high-altitude nurseries (Zobrist, 1950). In the study area under consideration, however, Herpotrichia produced a relatively benign and localized infection that apparently did little harm to the host trees. In