An Undescribed Fungus on Moss Capsules

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My attention was directed recently to the incidence of an ascomycetous fungus on the capsules of Mnium carolinianum Anderson. In an effort to identify this fungus account was taken of the imposing list of North American species (Seymour, 1929) known to occur in association with mosses. This list includes a variety of species, representing slime molds, phycomycetes, ascomycetes and basidiomycetes. Also the summary of species occurring on bryophytes prepared by Nicolas (1932) was consulted. This summary indicates that certain species have been established to be pathogenic, a few others are symbionts, but the larger number are manifestly saprobic. Evidence from observations indicates that the fungus herein considered is pathogenic. In examining any tuft of Mnium carolinianum one notes that among normal capsules are interspersed some that are shriveled and dried, and also that there are many naked setae, the capsules having been broken off. If one uses a dissecting microscope for closer inspection, scattered dark specks may be seen at the surface of affected capsules. When such capsules are teased apart, crushed under a cover glass, and examined with greater magnification, the dark specks are found to be perithecia. The perithecia are partly sunken within the capsule tissues, are globular, and have dark-brown, thin membranous walls. Each perithecium has a short papilla which marks the site of a prominent ostiolum. The perithecia range in diameter from 120-175 p. The asci tend to be fasciculate, are cylindric-clavate, and measure 50-60 X 6-7.5 y. The ascospores are closely compacted within the asci. They are straight or slightly curved, fusoid with acutely rounded tips, 3-septate, subhyaline, and range in size from 20-25 X 3-3.5 t. Paraphyses are lacking. The foregoing morphologic features are those of the pyrenomycetous genus Sphaerulina. Apparently no members of this genus have been recorded previously as occurring on any species of moss.