Difference between revisions of "Lescuraea"
in P. Bruch and W. P. Schimper, Bryol. Europ. 5: 101, plate 459. 1851.
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Revision as of 22:03, 16 December 2019
Plants small to medium-sized, in thin mats, yellow-green, gold-green, or green. Stems irregularly branched; paraphyllia many on branches, few on stems, filamentous to foliose, cells smooth or prorulose; rhizoids in clusters arising from base of stem leaves. Stem and branch leaves similar. Stem leaves appressed to julaceous when dry, erect-spreading when moist, ovate-lanceolate to lanceolate, strongly plicate proximally; margins recurved proximally, serrate distally, limbidium absent; apex abruptly to gradually acuminate, hair-point absent; costa single, 2/3 leaf length to subpercurrent, opaque, not sinuate; alar cells quadrate to short-rectangular; proximal laminal cells elongate, linear-fusiform, more than 3:1, walls somewhat pitted; medial cells linear-fusiform, 4–8:1, smooth or occasionally prorulose, walls thin. Specialized asexual reproduction absent. Sexual condition dioicous; perichaetial leaves pale translucent, squarrose when moist, longer, apex more acuminate, costa short. Seta 0.4–1.6 cm. Capsule erect, ovate to cylindric, symmetric; annulus absent; operculum conic; peristome strongly reduced; exostome teeth lanceolate or linear-lanceolate, papillose; endostome basal membrane low, segments slenderly lanceolate to filiform, cilia absent. Spores 14–22 µm, coarsely papillose.
Distribution
North America, Eurasia.
Discussion
Species 4 (1 in the flora).
Lescuraea is found mostly in montane to arctic-alpine regions. The four genera Lescuraea, Pseudoleskea, Ptychodium Schimper, and Rigodiadelphus Dixon 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 recognize the latter genus. Also, Rigodiadelphus is related to these three genera, and is probably closest to Pseudoleskea. If Rigodiadelphus is accepted, then it makes sense to segregate Pseudoleskea as well. Otherwise this would make Lescuraea in the broad sense paraphyletic. Lescuraea is here treated 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.