BFNA Title: Lescuraea
Author: J. R. Spence
Date: November 10, 2010
Edit Level: R
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

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XX. LESCURAEA Bruch & Schimper, Bryol. Eur. 5: 101 (fasc. 46-47. Monogr. 1). 1851 * (For Charles Léo Lesquereux, 1806--1889, Swiss-American bryologist and paleontologist)

John R. Spence


Plants prostrate, in thin mats, yellow-green, gold-green, or green. Stems slender, fragile, tips often ascending or hooked, irregularly branched; secondary branches appressed to ascending or erect, not flagelliform at tips; older primary stems becoming stoloniferous; paraphyllia common, filamentous to foliose, not much branched, cells smooth or prorulose, becoming scarce on older stems; rhizoids in clusters arising from base of stem leaves. Leaves of stems and branches similar but branch leaves smaller; leaves ovate to ovate-lanceolate, weakly to strongly concave, asymmetric, appressed to julaceous when dry, not catenulate, weakly falcate-secund, erect-spreading when wet, lustrous, lacking hair-point; lamina with 1(--2) distinct plications on each side of costa, apex abruptly to gradually acuminate, margins serrate distally, recurved proximally; costa moderately strong and 2/3 length of lamina to subpercurrent, not sinuose; mid-laminal cells linear-fusiform, 4--8:1, thin-walled, prorulose, laminal cells in acumen similar to more proximal cells, strongly prorate; alar cells quadrate to short-rectangular, smooth, juxtacostal cells elongate, linear-fusiform, mostly smooth, somewhat pitted. Specialized asexual reproduction absent. Sexual condition dioicous; perichaetial leaves pale translucent, longer and more acuminate, squarrose when wet, costa short. Capsule ovate to cylindric, erect, symmetric, operculum conic; annulus lacking; peristome double, strongly reduced, exostome teeth lanceolate or linear-lanceolate, papillose, not bordered, endostome with low basal membrane, segments slenderly lanceolate to filiform, not keeled, cilia absent. Calyptra cucullate. Spores small, papillose.


Species 4 (1 in the flora): Northern Hemisphere, mostly in montane to arctic-alpine regions.


The four genera Lescuraea, Pseudoleskea, Ptychodium and Rigodiadelphus form the core group of the family Pseudoleskeaceae Schimper, but the relationships among them have not been worked out. In the broad sense Lescuraea has generally included as synonyms both Pseudoleskea and Ptychodium, most European workers recognizing, however, the latter genus. Also, Rigodiadelphus is related to these three genera, and is probably closest to Pseudoleskea.  If Rigodiadelphis is accepted then it makes sense to segregate Pseudoleskea as well. Otherwise this would make Lescuraea in the broad sense paraphyletic.  I thus treat Lescuraea in the strict sense, excluding Pseudoleskea, based on numerous differences in leaf and capsule characters.  J. R. Rohrer (1986) provided a useful comparison of differences among the genera. M. U. Krieger has revised Lescuraea for North America in her M. Sc. thesis (University of Alberta, unpublished).


SELCTED REFERENCES Lawton, E. 1957. A revision of the genus Lescuraea in Europe and North America. Bull. Torrey Bot. Club 84: 281--307. Rohrer, J. R. 1986. Taxonomic notes on Rigodiadelphus, Ptychodium, and Okamuraea: three genera misplaced by Fleischer in the Rhytidiaceae. Lindbergia 12: 33-40.



1. Lescuraea saxicola (Schimper in P. Bruch, W. P. Schimper & W. Gümbel) Molendo, Moostud. 144, 147, 149. 1864


Lescuraea striata var. saxicola Schimper in P. Bruch, W. P. Schimper & W. Gümbel, Bryol. Eur. 5: 103. pl. 459 (fasc. 46--47. Monogr. 2, plate 1). 1851; L. iliamniana E. Lawton; L. julacea Bescherelle & Cardot.


Plants green to yellow-green, older stems golden or orange. Stems weakly appressed to substrate; irregularly branched, secondary branches common, curved to erect, often hooked at tip; paraphyllia usually numerous on branches, less common on primary stems, but sometimes nearly absent. Leaves of primary stems 0.7--1.4 mm, mostly ovate-lanceolate but irregular, sometimes lanceolate, distinctly asymmetric, strongly plicate proximally; costa orange at least at base, serrulate abaxially distally; median laminal cells 14--50 x 4--7 /um, slightly shorter and wider proximally, cells typically smooth, alar region small, cells quadrate to short-rectangular, thin walled, mostly smooth; leaves of branches smaller, median and distal cells more strongly prorulose. Seta 0.4--1.6 mm, slender, yellow-orange, flexuose. Capsule 1--2 mm, yellow-orange to red-brown. Spores 14--22 /um, coarsely papillose.


Capsules rare, mature summer (Jul--Aug). Locally common on granitic or sandstone boulders or outcrops and exposed mineral soils, often in seepage areas in primarily subalpine and Arctic-alpine regions; 250--3400 m; Greenland; Alta., B.C., Nfld. & Labr., Que., Yukon; Alaska, Colo., Nev., Utah, Vt., Wash.; n Europe; Asia (n Russia, China, India, Japan).


Lescuraea saxicola is distinguished from most Pseudoleskea species by the elongate, thin-walled median laminal cells, and from Psuedoleskea baileyi in lacking a hair-point.