BFNA Title: Brachelyma
XX. BRACHELYMA Schimper ex Cardot, Mém. Soc. Sci. Nat. Cherbourg 28: 130. 1892 * [Greek brachys, short, and elyma, veil, alluding to diminutive calyptra]
Bruce H. Allen
Plants slender to medium-sized, submerged or seasonally inundated. Stems prostrate or pendent, irregularly branched, in cross section with a very thick scleroderm, firm-walled cortical cells, no central strand; axillary hairs 240--360 \um, basal 1--3 cell(s) subrectangular, reddish brown, distal 3--5 cells oblong, hyaline; rhizoids from clusters of initials abaxial to the leaf insertions, not or weakly branched. Leaves 3-ranked, crowded and imbricate, distant and erect to erect-spreading, keeled and conduplicate, oblong-lanceolate to lanceolate, obtuse to acute, decurrent; margins entire or serrulate proximally, serrulate to serrate at apices, at times narrowly reflexed; median leaf cells rhomboidal, linear-rhomboidal or elongate; marginal cells linear, forming a weak border; alar cells firm-walled, quadrate or rectangular, not or slightly enlarged, costa usually subpercurrent to percurrent. Sexual condition dioicous; perigonia gemmate, lateral in leaf axils, perigonial leaves ecostate, antheridia few (4--5), paraphyses present; perichaetial leaves elongate, sheathing the setae, archegonia numerous, paraphyses present. Seta short, surface cells quadrate. Capsule immersed, oblong-cylindrical to oval; operculum long-conic at times obliquely beaked; annulus massive; stomata absent; peristome with exostome teeth inserted, shorter than endostome, linear, orange or red, trabeculae widely spaced, papillose, more strongly thickened on the inner surface than the outer surface; endostome segments linear, red to brownish-orange, papillose, joined by lateral bars only at the apex (trellis imperfect). Calyptra cucullate, covering only the operculum.
southeastern and central
Brachelyma is a monotypic genus endemic to eastern
REFERENCES Cardot, J. 1892. Monographie des Fontinalacées. Mém. Soc. Sci.
Nat. Cherbourg 28: 1--151. Welch, W. H. 1960. A monograph of the
1. Brachelyma subulatum (Palisot de Beauvois) Cardot, Mém. Soc. Sci. Nat. Cherbourg 28: 130. 1892
Fontinalis subulata Palisot de Beauvois, Prodr. Aethéogam. 58. 1805; Dichelyma subulatum (Palisot de Beauvois) Myrin; Brachelyma robustum (Cardot) E. Britton
Plants green, yellowish green to brown, dull. Stems to 30 cm, irregularly branched. Leaves 2--4 mm; median leaf cells 10--60 x 5--8 \um, marginal cells 60--120 x 6--8 \um; alar cells quadrate or rectangular, slightly enlarged, costa subpercurrent to percurrent. Perichaetial leaves ovate-lanceolate to linear-lanceolate, 2--4 mm, acute to long-acuminate, entire, ecostate. Seta 0.7--1.5 mm. Capsule 1.5--2.5 mm; operculum 0.5--1.2 mm; annulus of 8--9 rows of thick-walled cells, persistent on capsule mouth after dehiscence. Calyptra smooth, naked, 2--3 mm. Spores 13--18 \um, minutely roughened to smooth.
Tree trunks, branches, roots, bushes, logs, soil, and rocks along rivers or in flood plains and sloughs, subject to inundation; 4--271 m; Ala., Ark., Fla., Ga., Ill., Ind., Ky., La., Md., Miss., Mo., N.C., Okla., S.C., Tenn., Tex., Va.
Brachelyma subulatum differs from all Fontinalis species in having costate leaves and cucullate calyptrae. Usually the presence of costate leaves is enough to separate the two genera, but costal expression in Brachelyma is sometimes variable and appears to be environmentally induced. It is not unusual to find plants with keeled, strongly costate proximal leaves but concave, ecostate or weakly costate apical leaves. Brachelyma subulatum has been noted as lacking an annulus, but in fact it has massive, persistent annulus quite similar to the annulus found in many genera of the Hookeriales. Dichelyma differs from Brachelyma subulatum only in having longer setae and larger calyptrae that completely cover the capsule and often clasp the distal portion of the seta. Brachelyma subulatum appears to be only a weak segregate of Dichelyma. In the absence of prior experience with Brachelyma subulatum, the species could be confused with many other aquatic or semi-aquatic mosses. But, B. subulatum differs from all of such mosses in having keeled-conduplicate leaves.