DISCINELLA SCHIMPERI, A CIRCUMPOLAR PARASITE OF SPHAGNUM SQUARROSUM, AND NOTES ON BRYOPHYTOMYCES SPHAGNI

SUMMARY Apothecia and cultures of Discinella schimperi comb. nov. (= Helotium schimperi) are described from North American material. It has distinctive haustoria which parasitize a type of secretory cell in Sphagnum squarrosum. The presence of these haustoria in herbarium specimens indicates that D. schimperi is a common circumpolar species occurring in Europe, the U.S.S.R., Japan, Canada and the U.S.A. Evidence indicating that Bryophytomyces sphagni is a distinct fungus is presented. A bryological enigma was partially resolved when Nawaschin (1888) described Helotium schimperi, a minute, highly specialized ascomycetous parasite of Sphagnum squarrosum Crome. By careful dissection and keen observations of the host's capitulae he was able to trace mycelium from the sessile apothecia on the phyllids to mucilaginous cells in the phyllid's axils. An unusual mode of attack of these mucilaginous cells by appresoria and haustoria was discovered and described with accompanying illustrations. The wefts of mycelium between the caulids and phyllids were thought to be homologous to the "paraphyses" described by Schimper (1858). At a later date, Nawaschin (1890) partially resolved a second bryological enigma previously noted by Schimper (1858). Nawaschin described Tilletia sphagni, a smut-like fungus which produced spores in the capsules of Sphagnum, usually replacing the moss spores. The spores were thought to be homologous with the microspores previously attributed to the host. Ciferri (1954) proposed the name Bryophytomyces to accommodate T. sphagni which he did not believe was congeneric with Tilletin. The name Helotium schimperi might well have passed into obscurity unlike the name Bryophytomyces sphagni (Naw.) Ciferri which attracted attention because of the implications for the origin of 904