Brachymenium ayangannensis H.Rob. & G.K.Golinski, 2020

Robinson, Harold & Golinski, G. Karen, 2020, Notes on Brachymenium in Guyana with a new species from Mt. Ayanganna, PhytoKeys 154, pp. 11-17 : 11

Brachymenium ayangannensis H.Rob. & G.K.Golinski sp. nov. Figure 1

Type.

Guyana. Region: Potaro-Siparuni. Mt. Ayanganna, east face, plateau above second of four escarpments. 1380 m, 05°22.550'N, 059°58.350'W. Scrub forest on sandstone and peat, with Clusia , Pagamea and Sphagnum . Epiphyte; sporophytes green. 17 June 2001. H.D. Clarke 9299, with R. Williams, C. Perry, E. Tripp & J. Kelly (US).

Description.

Stems up to 3 cm tall, leaves not closely spaced, rather firm in structure but contorted when dry and resistant to wetting. Costa percurrent into a long slender acumination, median cells narrowly oval, with firm walls showing slight porosity, mostly 80-100 μm long and ca. 30 μm wide, without shorter quadrate cells at base, margin with numerous rows of linear pale cells forming a strong border, border with numerous cells projecting as spiniform teeth, such spiniform teeth extending onto apical acumination. Synoicous? Seta pale yellowish-red, ca. 17 mm long, smooth. Capsules erect, ca. 2 mm long, with short hypophysis, operculum short-rostrate, higher than wide. Outer peristome teeth reddish, rudimentary, ca. 80 μm long, inner peristome a low pale membrane ca. 70 μm without projecting segments or cilia. Calyptra not seen. Spores ca. 10 μm in size.

Additional material.

Guyana. Region: Potaro-Siparuni. Mt. Ayanganna, east face, area near camp at base of fourth of four escarpments. Elev. 1545 m, 05°23.083'N, 059°58.550'W. Dense forest on sandstone and peat, with Euterpe , Clusia , and Brocchinia . Sporophytes green. On tree limb. H.D. Clarke 9551 with R. Williams, C. Perry, E. Tripp & J. Kelly (US).

The peristome teeth of the new species have proven extremely fragile, possibly because of the radiation treatment.

The spiniform teeth of the leaf margin are distinctive, but the manner in which they occur on the acuminate apical extension is reminiscent of the illustration by Brotherus (1904: 557 fig. C; 1925: 367, figs C, D). This illustration has led to the comparison, but it proves to be somewhat inaccurate compared to the more recent illustration made from the type by Ochi (1972)

The African species is well illustrated by Ochi (1972), but the type from Helsinki has been borrowed not because of doubts of relationship so much as to insure that the two species are not the same. The principle difference is the absence of spinose teeth extending on to the apical acumination of the leaf. Nevertheless, there is no doubt the two are close, and the African species was placed in Bryum only because there was no sporophyte to indicate otherwise. A important point derived from the Ochi study is that none of the species in typical Bryum have spinose marginal teeth, all with such teeth are in what is now in the Brachymenium , Rhodobryum relationship. On the basis of the evident relationship between the African and Guyana species, the following transfer of the African species is provided.

Figures

Figure 1. Brachymenium ayangannensis H. Rob. & G. K. Golinski. A Leafy stem showing distorted leaves B distal part of leaves, showing well-developed pale margin and spiniform teeth on both margin and long-acuminate tip C remoistened erect capsule showing partially detached short-rostrate operculum D B. perspinidens (Broth.) H. Rob. & Golinski, distal part of leaf of holotype (from H) E tip of capsule mounted in Hoyer's solution showing short exostome and lack of well-developed endostome. The photographs were taken using a Leica DM 4 B Compound microscope, using a 5 x objective.