DISTRIBUTION AND SYSTEMATICS OF BATRACHOSPERMUM (BATRACHOSPERMALES, RHODOPHYTA) IN NORTH-AMERICA .4. SECTION VIRESCENTIA

Thirty-nine populations of Batrachospermum section Virescentia from No rth America were compared to eight type specimens and two historically important specimens using multivariate morphometrics and image analys is. From this analysis, two species are recognized: B. helminthosum Bo ry de Saint-Vincent (syn. B. bruziense Sirodot, B. graibussoniense Sir odot, B. sirodotii Skuja ex Flint, B. testale Sirodot, B. virgatum Sir odot nom. illeg., and B. viride Sirodot) and B. elegans Sirodot (syn. B. coerulescens Sirodot nom. illeg.). In B. helminthosum trichogynes a re cylindrical to slightly club-shaped with few to no protuberances, w hereas in B. elegans half to all of the trichogynes have one to three basal knobs or branches. None of the qualitative features previously u sed to separate species in this section were found to be of taxonomic value due to their universal presence; quantitative characteristics we re highly variable and overlapped among specimens examined. Emended de scriptions of both species are provided. Batrachospermum elegans was c ollected in northeastern U.S.A. and central Costa Rica, whereas B. hel minthosum ranged from Nova Scotia to Louisiana and was collected in ce ntral Mexico, Costa Rica, and northwestern U.S.A. Batrachospermum juli anum Arcangeli and B. transtaganum Reis, previously classified in sect ion Virescentia, were observed to have twisted carpogonial branches an d, therefore, should be placed in section Contorta. Sections Setacea a nd Virescentia of Batrachospermum differ in whorl size, ratio of carpo sporophyte height to whorl diameter, and trichogyne stalking; hence, w e continue to recognize them as being distinct taxonomic entities as o riginally described.