BFNA Title: Roellia
Author: J. Spence
Date: February 21, 2008
Edit Level: R Brum+
Version: 3

Bryophyte Flora of North America, Provisional Publication


Return to Home

XX. ROELLIACEAE J. R. Spence & H. P. Ramsay


John R. Spence

Plants acrocarpous. Stems  rosulate, unbranched, stolons absent; rhizoids sparse, confined to stem base, micronemata and macronemata absent. Leaves large, broadly ovate to obovate, base more or less straight at insertion, decurrent, laminal surface finely rugose; margins plane distally,  revolute proximally, serrate in distal half, rarely nearly entire, 1-stratose, limbidium present, well developed, apex acute, sometimes mucronate, costa slender, green-yellow, percurrent, transverse section with reduced stereid band or stereids nearly absent; basal adaxial supracostal cells long-rectangular, laminal cells large, obscurely heterogenous, proximal cells long-rectangular,  longer than distal cells, medial cells generally similar to distal cells, distal cells hexagonal to rhomboidal, not oblique to the costa, thin-walled, walls not distinctly pitted, alar cells  similar to juxtacostal cells. Specialized asexual reproduction absent. Sexual condition dioicous; perigonia and perichaetia terminal, perigonia enlarged, forming a rosette, inner leaves highly differentiated, often narrower with a weaker costa. Seta 1(--2). Capsule nutant, long-exserted, long-pyriform to elongate-cylindric, sometimes curved, hypophysis well-differentiated; annulus present, revoluble; operculum convex, short-conic; peristome diplolepidous-alternate, exostome teeth lanceolate-acuminate, papillose, narrowly bordered, trabeculate, lacking pores, endostome free, pale, with high basal membrane, segments keeled, perforate, cilia long, (2--)3--4, nodose. Calpytra fugacious, cucullate, small, smooth. Spores shed singly, small, 10--18 \um.


Genus 1: w North America.


Roellia is a large, distinctive monotypic endemic moss found in high elevation and other cool-climate forests of western North America, where it typically occurs on litter under dense shade.  The taxonomic placement of R. roellii has long been debated.  Early workers placed the species in either Mnium or Bryum, while more recently it has been segregated as the monotypic genus Roellia and placed in the Bryaceae, primarily because of its distinctive laminal areolation.  Although Roellia is morphologically similar to Rhodobryum and Rosulabryum, recent molecular studies suggest that it is closer to the Mniaceae than the Bryaceae.  Superficially, under the light microscope, the species looks distinctly mniaceous.  It is best placed in its own family.  Roellia is similar to species of Rhodobryum of the flora, but differs in its much larger lamina cells, and leaves that are rugose and shrunken but not strongly contorted and twisted when dry.


1. ROELLIA Kindberg, Gen. Eur. & North Amer. Bryin. 37. 1897


Plants robust, as scattered individuals, or forming open turfs, usually pale green. Leaves shrunken to imbricate or somewhat contorted when dry, erect-spreading when wet, laminal cells 2--4:1.  Seta long, straight, yellowish, becoming red-brown with age. Capsule brown, exothecial cells near mouth quadrate or short-rectangular, thick walled, often reddish, in 4--5 rows, proximal cells longer, long-rectangular with somewhat sinuose walls. Spores smooth to finely papillose, pale yellow-brown.


Species 1: w North America.


1. Roellia roellii (Röll) H. A. Crum, Bryologist 70: 107. 1967


Mnium roellii Röll, Bot. Centralbl. 44: 420. 1890; Bryum lucidum E. Britton; B. sandbergii Holzinger; Mnium lucidum (E. Britton) Brotherus; Roellia lucida (E. Britton) Kindberg; R. simplex (Macoun & Kindberg) Kindberg


Stems 1--4 cm. Leaves sometimes tinted pink or red below, small and scale-like proximally, enlarged above, rosette leaves 4--7 mm; lamina cells 90--150 x 30--50 \um, cells along margin narrower and thicker walled, forming a somewhat distinct border of 2 layers, basal cells more regularly rectangular, often somewhat narrower and longer than distal cells. Perigonia conspicuous, with abundant yellow antheridia in disk-like heads. Perichaetial leaves similar to stem leaves, somewhat smaller. Capsule 4--7 mm.


Capsules rarely produced, mature summer--fall (July--September). Litter and rich humus under trees and shrubs, mostly montane and subalpine coniferous forests; 0--3200 m; Alta, B.C.; Alaska, Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.


Roellia roellii is rare in Alaska, Nevada, and Utah, and is most common in areas south of the Pleistocene ice-sheets in western North America. Coastal Alaskan-northern B.C. populations probably survived glaciation in refugia. It has been found near sea level in coastal Alaska but generally occurs at 500--3200 m.