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BFNA Title: Macrocoma |
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Macrocoma
- Orthotrichaceae 4.
Macrocoma (J. K. A. Müller) Grout, Bryologist 47: 4. 1944 * [Greek macro-, long, and kome, maine, alluding to long hairs on
calyptrae of some species] Macromitrium sect. Macrocoma J. K. A. Müller, Bot. Zeitung (Berlin) 3: 522. 1845 Dale H. Vitt Plants slender to filiform, mats on trees
and rocks. Stems creeping with numerous lateral ascending branches.
Branch leaves closely erect-appressed, not contorted when dry,
erect-spreading when moist, up to 2 mm, lanceolate to ovate-lanceolate,
narrowly obtuse, acute, or bluntly acuminate, carinate, rhizoids often
produced on the abaxial side of the costa; margins ± plane, entire; costa percurrent, prominant; distal cells
small, rounded-quadrate, bulging, smooth or papillose; basal cells rounded to
elliptic, bulging, papillose-mammillose.
Perichaetial leaves slenderly
acute. Sexual condition goniautoicous.
Seta smooth, to 7 mm,
dextrose. Capsule exserted, oblong-cylindric to fusiform, ± plicate above or smooth; stomates superficial; peristome
single or lacking; consisting of 16 pale, short, blunt teeth or a low,
papillose membrane. Calyptra
mitrate, long elliptic-conic, ±
hairy, completely covering capsule, smooth.
Spores rather large,
isomorphic. Species
11 (1 in the
flora); in higher elevation scrub forests; North, Central and South America,
West Indies, Asia, Africa (including Madagascar), Australia, Pacific Islands
(Hawaii, New Zealand). In
addition to the rounded basal cells, characters of the genus include the
slender, irregularly branched stems, leaves erect-appressed when dry, capsule
cylindric, peristome often reduced, and calyptra long conic-elliptic. 1.
Macrocoma tenuis (Hooker
& Greville) Vitt, Rev. Bryol. Lichénol. 39: 217. 1973 Orthotrichum
tenue
Hooker & Greville, Edinburgh J.
Sci. 1: 120. plate 5. 1824 Subspecies
2 (1 in the flora): North America; Central America; South America; West
Indies; Asia; s Africa; Pacific Islands (New Zealand); Australia. 1a.
Macrocoma tenuis subsp. sullivantii
(J. K. A. Müller) Vitt, Bryologist 83: 405--436. 1980 'Macrocoma sullivantii J. K. A. Müller, Bot. Zeitung
(Berlin) 20: 361. 1862 Plants slender. Branch
leaves 0.7--1.2 mm, acute to narrowly obtuse; cells papillose, up to 22
µm, margins of distal cells bulging. Perichaetial leaves longer. Seta
4--6.5 mm. Capsule 1.3--2 mm; exothecial cells not or slightly
differentiated; peristome single, consisting of low, densely papillose
membrane. Calyptra obscurely plicate, mitrate but many times splitting by
single cleft along one rib. Spores
33--42 µm. Dry
mountain tops and slopes of the southern Blue Ridge escarpment, abundant,
sometimes covering entire tree trunks of Pinus,
Juniperus, and Quercus; 600 m
and above; Ga., N.C., S.C., Tenn.;
Mexico; West Indies; South America; Asia (China, Japan, Korea, Taiwan). Macrocoma tenuis subsp. sullivantii differs from other species in the Orthotrichaceae
by having slender, creeping stems with erect branches. The leaves are erect-appressed, and the
basal cells of the leaves are rounded-quadrate. It is very closely related to a Mexican
species, M. orthotrichoides, which
differs in having a peristome and its sparsely hairy calyptra. Macrocoma
tenuis subsp. tenuis is Old
World in distribution. |
