NSF-PEET Project in Systematic Bryology

Special Project

Revision of the Moss Genus Rhynchostegiopsis C. Mull. (Leucomiaceae)

for NSF-PEET training at Missouri Botanical Garden

Michelle Judith Price



Generic Description


Keys to Species

Digital Images of Species

Names in Rhynchostegopsis

Distribution Maps


Rhynchostegiopsis was first described by Carl Muller in 1897 based on a specimen from Bolivia. It currently contains five species (R. brasiliensis, R. carolae, R. costaricensis, R. flexuosa and R. tunguraguana). The genus is restricted to the neotropics. It is found from southern Mexico, Central America, the Caribbean, northern South America and southeastern Brazil. Plants are found in damp habitats usually on decayed logs, soil and less frequently on roots and trees in montane forest zones.

Rhynchostegiopsis is marked by: (1) serrate leaf margins; (2) lax and elongate median cells; (3) two celled axillary hairs; (4) furrowed exostome teeth that are horizontally striate below; (5) well developed endostomial cilia; (6) rostrate operculae; and (7) cucullate calyptrae.

The genus lacks: (1) costae; (2) alar development; (3) pseudoparaphyllia; (4), paraphyllia; (5) leaf cell ornamentation; (6), central strands; and (7) a hyalodermis.

The characters that are 'lacking' in combination with the morphological characters that are present in the genus help define Rhynchostegiopsis and align it with the Leucomiaceae. Rhynchostegiopsis is interesting since it shares morphological features with two large families, the Hookeriaceae and the Hypnaceae. Five species are recognised in Rhynchostegiopsis in this work and the genus has been maintained in the Leucomiaceae (Hookeriales) based on the gametophytic features it shares with other genera in this small family (Leucomium, Tetrastichium and Philophyllum).


Generic Description

Plants small to large, glossy, pale green to yellow-green or golden with age; forming dense to thin mats.Stems fragile to sturdy, sometimes dark coloured, creeping or spreading, subpinnately to irregularly branched, complanate-foliate, lateral and dorsal leaves often slightly differentiated; in cross-section cells homogeneous, large and thin-walled, central strand absent, hyalodermis lacking; paraphyllia and pseudoparaphyllia absent; axillary hairs two-celled, basal cell small and brown, upper cell enlarged and hyaline; rhizoids dark red, smooth, clustered underneath stem, at base of and abaxially to the leaf insertion. Leaves spreading, erect spreading or falcate, usually crowded, not much contorted wet or dry, symmetric, not decurrent; lanceolate, oblong-lanceolate, ovate to ovate-lanceolate, flat to slightly concave below, flat above, apices short to long-acuminate or flexuose; lamina unistratose; margins plane, entire below, sharply serrate to serrulate above to sometimes sub-entire; ecostate; laminal cells smooth, walls non-porose; median leaf cells lax to firm, long-linear to long-hexagonal throughout; alar cells un-differentiated; basal cells slightly broader and longer than median cells; upper marginal cells conspicuously or slightly enlarged in comparison to median cells. Asexual propagula infrequent, in clusters on dorsal leaf surface. Dioicous. Perigonia lateral, leaves smaller than but otherwise similar to perichaetial leaves. Perichaetia lateral, conspicuous or inconspicuous; leaves erect with spreading apices, ovate to ovate-lanceolate, apices almost entire to serrate, sometimes flexuose; ecostate; median cells long-hexagonal to long-linear, basal cells shorter and broader, alar cells not differentiated. Setae singular, long, smooth to sometimes roughened just below base of capsule, reddish to dark red. Capsules exserted, inclined, horizontal to pendant; cylindric, smooth, neck undifferentiated; exothecial cells subquadrate to short rectangular, collenchymatous with horizontal walls usually thicker than vertical walls; stomata at base of urn, superficial; opercula long-rostrate from a conic base; annulae with several rows of cells, deciduous. Peristomes double, exostome teeth 16, narrowly-triangular, finely papillose above, front with narrow median line, plates densely horizontally striate; endostome basal membrane high, segments 16, narrowly triangular, almost as long as exostome teeth, keeled, smooth to finely papillose, often narrowly perforate, cilia 1-2(3). Calyptrae cucullate, naked, smooth. Spores spherical, finely papillose.



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Pages Designed by Michelle Price, April 2000.