Observations on Species of Phymatotrichum

INTRODUCTION. The genus of fungi, Phymatotrichum, has remained obscure except for the species, P. omnivorum which causes a root rot of more than 2,000 species of dicotyledonous plants in the southern and southwestern United States and northern Mexico. Interest in the taxonomic and evolutionary position of Phymatotrichum species has increased following the discovery of a sexual stage of P. omnivorum (Baniecki and Bloss, 1969b). The present discussion is an attempt to assemble the available species and to distinguish the characteristics which constitute the genus.