Racomitrium ryszardii (Musci, Grimmiaceae), a new hydrophilous species from the Pacific Northwest with comments on Racomitrium aquaticum in North America

Racomitrium ryszardii Bedn.-Ochyra from western Noah America is described a nd illustrated. It belongs to subg. Cataracta Vilh. sect. Stenotrichum (Che v.) Bedn.-Ochyra and is closely related to R. aquaticum (Schrad.) Brid. wit h which it constitutes subsect. Hydrophilum Bedn.-Ochyra. It differs from R . aquaticum in its keeled, linear-lanceolate leaves, the absence of a basal marginal row of pellucid cells, a cristate leaf apex, long costa extending almost to the apex, an anatomical structure of the costa and longer perist ome teeth. It is a hydrophytic moss growing from sea-level to subalpine ele vations on outcrops and boulders near streams through the coastal coniferou s forest from north Oregon to south-eastern Alaska. All collections of R. r yszardii have formerly been reported from the Pacific Northwest as R. aquat icum and the only exception is the specimen from Montana which has not been available for examination. The only record of the latter species from east ern North America is also based on misidentification, and the voucher speci men actually belongs to R. sudeticum (Funck) Bruch & Schimp. Accordingly, R . aquaticum must apparently be withdrawn from the moss flora of North Ameri ca, unless the specimen from Montana represents this species. (C) 2000 Adac / Editions scientifiques et medicales Elsevier SAS.