Title: Gemmae on leaves and other observations regarding Bryum flaccidum Brid.
Abstract:On a trip to the Bruce Peninsula, Ontario, during the summer of 1997, I collected some Orthotrichum on a roadside Sugar Maple (Acer saccharum).Under the dissecting microscope, my curiosity turned inst...On a trip to the Bruce Peninsula, Ontario, during the summer of 1997, I collected some Orthotrichum on a roadside Sugar Maple (Acer saccharum).Under the dissecting microscope, my curiosity turned instead to a few very small, bright green plants hiding in a crevice.Despite a rather striking combination of characteristics, I was unable come to a satisfactory determination.I searched the manuals in vain for something combining broadly ovate leaves, a costa ending well short of a hyaline awn, entire and bordered margins, and gemmae on the leaves and in the axils.The gemmae were cylindrical and several cells in length and could be found scattered across both surfaces of some leaves, as well as in the leaf axils (Fig. 1).Eventually, I recognized that I was dealing with Bryum capillare Hedw.or something closely related to it.On comparing various manuals at hand, I was struck by the range of variation, the number of subordinate taxa and synonyms, and the often-contradictory characters attributed to this species.However, none of these references illustrates or describes gemmae on the leaves of this or any other Bryum.Nor did the small size of my specimens fit the range given for B. capillare.Most illustrations showed the costa extending into the tip, quite unlike my find.In most other respects, it matched reasonably well.By this time, I had returned to the site of my original collection and found more plants.I forwarded some of this material (533a, Nov. 1997, near Hepworth, Grey Co., ON: MICH) to Howard Crum at the University of Michigan.He confirmed the presence of the gemmae on the leaves and indicated that the specimen could be referred to either Bryum flaccidum Brid.or to B. capillare var.flaccidum (Brid.)Bruch.& Schimp in B.S.G.For the sake of brevity, I will employ the specific rank, although I harbor some misgivings as to its appropriateness.A few additional specimensRead More