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BFNA Title: Brachymenium |
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BRACHYMENIUM
– BRYACEAE XX.
BRACHYMENIUM Schwägrichen, Sp. Musc. Frond. Suppl. 2(1): 131. 1824 * [Latin brachy, short, and menium, a membrane,
alluding to poor development of endostome] John R. Spence Plants small, forming dense turfs or
cushions, green to red-green. Stems
short, 0.3--1.5 cm, sometimes rosulate, sparsely to strongly branching by
subfloral innovations, rhizoids sparse to abundant, variously colored, smooth
to papillose, micronemata often present on stems. Leaves irregularly contorted to spirally twisted around stem when
dry, erect-spreading when wet, broadly ovate, 1--2.5 mm, smaller proximally, leaf
base not curved at insertion, not or only weakly decurrent; margins plane or
revolute proximally, 1-stratose, limbidium absent or present, distal margins
serrulate to serrate, apex broadly rounded, apiculus absent, costa shortly to
moderately long-excurrent in a stout denticulate, colored awn, transverse
section with stereid band single, well
developed, guide cells present; adaxial supracostal cells irregularly to
regularly quadrate or short-rectangular at leaf base, laminal cells
heterogenous, proximal cells usually quadrate, distinctly different in shape,
medial cells generally similar to distal cells, distal cells short-rectangular
to irregularly hexagonal, 1.5--3:1, not in rows oblique to the costa, thin-
to somewhat thick-walled, walls not pitted, alar cells usually similar to
juxtacostal cells. Specialized asexual
reproduction by spherical rhizoidal tubers and bulbils in leaf axils. Sexual condition dioicous; perigonia
and perichaetia terminal, leaves the same size as vegetative leaves or
typically larger, sometimes forming a rosette, inner leaves highly
differentiated, often narrower with a weaker costa. Seta single, variously colored, long, straight. Capsule erect to suberect, ovate to
cylindric, wrinkled when mature, hypophysis well-differentiated, rugose,
operculum short to tall-conic; peristome double, exostome red-brown
proximally, pale distally, papillose, teeth linear-lanceolate, separated at
base, endostome of basal membrane hyaline to pale yellow, low, segments
absent or short and blunt. Spores
shed singly, 12--18 \um, smooth or papillose, pale tan to brown. Species
ca. 30 (1 in the flora): worldwide in tropical and subtropical regions,
primarily Paleotropical. The
genus Brachymenium was originally based on the erect capsule with a
variously reduced peristome, but recent research indicates the genus to be
highly polyphyletic. Apparently this
sporophytic syndrome has evolved independently several times in groups with
distinctive gametophytes. I have used
gameophyte morphology as the basis for re-assigning sections and species to
other genera. Typical Brachymenium consists of subtropical-tropical
epiphytes with gametophytes similar to those of Rosulabryum. The type species is B. nepalense
Hooker ex Schwägrichen. Brachymenium
andersonii is re-assigned to Rosulabryum, while the small species B.
exile Dozy & Molkenboer and B. mexicanum Montaigne are placed
in Gemmabryum near the G. bicolor complex. Finally, B. systylium is transferred
to the newly erected genus Leptostomopsis, of which it is the type.
The only remaining North American species, B. macrocarpum, is probably
not closely related to the type section of Brachymenium. H. Ochi
(1980) placed it in section Peromnium, along with B. regenellii
Hampe and B. jamesonii Tayloy This group is similar to some species of
Gemmabryum, especially the Paleotropical G. coarctatum (Bosch
& Sande Lacoste) J. R. Spence & H. A. Ramsay, but differ in the
presence of bulbils and strongly rosulate and twisted leaves. Because of the uncertainty with the
phylogenetic relationships of the section, I have tentatively retained it in Brachymenium
pending further study. The genus description above is based on Brachymenium
sect. Peromnium (Mitten) Broth. SELECTED
REFERENCES: Ochi, H. 1980. A revision of the Neotropical Bryoideae, Part 1.
J. Faculty Educ. Tottori Univ., Nat. Sci. 29: 49--154. Spence, J. R. 2006. New combinations in the
Bryaceae (Bryophyta) for 1. Brachymenium macrocarpum Cardot, Rev. Bryol. 38: 6. 1911 Plants 1--2 cm, strongly branched and forming
dense dark green to olive green cushions. Leaves ovate, 0.6--1.5 mm,
somewhat concave, spirally twisted around stem when dry, forming rosettes
when wet; margins weakly revolute proximally, plane distally, distinctly
serrate, apex broadly rounded-acute; costa short-excurrent into a stout
somewhat yellowish-hyaline denticulate hairpoint; distal and median laminal
cells hexagonal to short-rectangular, 2--3:1, proximal cells quadrate, 1--2
rows of somewhat elongate cells forming an ill-defined limbidium. Specialized asexual reproduction of rhizoidal tubers, spherical, 100--300 \um,
red to orange-red, commonly on rhizoids at base of stem. Sexual condition dioicous. Seta 1--2 cm, light brown to
red-brown. Capsule 1--3 mm, elongate ovate to subcylindrical,
distinctly wrinkled when dry. Spores pale brown, more or less smooth,
15--17 \um. Capsules
mature spring--summer (Apr--Aug). Uncommon on tree trunks, wood and
occasionally rock, rarely on mineral soil; 0--1000 m; Brachymenium macrocarpum is a distinctive species that,
within its range, should be easy to identify. It forms dense turfs or
cushions on trees and rocks. The very
similar B. klotzschii (Schwägrichen)
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