XX. BRYOLAWTONIA Norris & Enroth, Bryologist 93: 328--331 * [For Elva Lawton, 1896--1993, American bryologist]
Daniel H. Norris
Plants frondose. Stems: primary stems stoloniferous with microphyllous or heavily eroded leaves, secondary stems decumbent, sometimes appearing prostrate, pinnately branched mostly in a single plane, with branches similar one to another; paraphyllia absent, pseudoparaphyllia short and broad, denticulate on margins. Leaves complanate, ovate to elliptic, margins plane but with some recurvature at and sometimes before mid leaf , serrate beyond the middle; costa single, ending before leaf apex; lamina cells thick-walled, smooth, median cells short-elliptic, with rounded lumens, alar cells quadrate to transversely elongate in a large group. Seta smooth and erect, to 15 mm. Capsule exserted, cylindric. Peristome teeth 16, horizontally striate, linear; endostome well-developed but shorter than exostome, segments perforate, cilia 2, appendiculate.
Species 1 (1 in the flora); w North America.
Bryolawtonia has complanate leaves with broadly rounded, serrulate margins. In the field, Bryolawtonia can be confused with Dacryophyllum falcifolium, an endemic genus of the Hypnaceae restricted to the Central California coast. Dacryophyllum is similar in size to Bryolawtonia but differs in possessing cultriform-asymmetric leaves unlike the almost symmetric-leaved Bryolawtonia. Porotrichum bigelovii of west coastal North America has complanate leaves with broadly rounded, dentate apices but that plant is markedly larger than Bryolawtonia, and has leaves appearing asymmetric as a result of broad recurvature of the postical margin. Bryolawtonia is a recent generic name for a plant once called Bestia vancouveriensis, a plant with a long nomenclatural history (D. H. Norris and E. J. Enroth (1990). There are few similarities between the plants in these two now accepted monotypic genera.
SELECTED REFERENCES: Lawton, E. 1971. Moss Flora of the Pacific Northwest. Nichinan. Norris, D. H. and E. J. Enroth. 1990. Description of Bryolawtonia Norris & Enroth with observations on the Genus Bestia. Bryologist 93: 328--331. Norris, D. H. and J. R.Shevock. 2004. Contributions toward a bryoflora of California. II. A key to the mosses. Madroño 51: 133--269.
1. Bryolawtonia vancouveriensis (Kindberg) D. H. Norris & E. J. Enroth, Bryologist 93: 328--331. 1990
Thuidium vancouveriense Kindberg, Bull. Torrey Bot. Club 17: 277. 1890; Bestia holzingeri (Renauld & Cardot) Brotherus; B. occidentalis (Kindberg) Grout; B. vancouveriensis (Kindberg) Wijk & Margadant; Heterocladium vancouveriense (Kindberg) Kindberg; Hypnum occidentale Sullivant & Lequereux; Isothecium occidentale (Kindberg) R. S. Williams;Porotrichum vancouveriense (Kindberg) H. A. Crum; Pseudoleskea occidentalis Kindberg; Pseudoleskeella vancouveriensis Kindberg) Kindberg; Thamnium vancouveriense (Kindberg) E. Lawton; Thamnium holzingeri Renauld & Cardot
Plants small, glossy dark-green to olive or brownish green. Stems: an inconspicuous prostrate and microphyllous stolon giving rise to a series of plumose decumbent to ascending axes to 3 cm; stem transverse section with 4--5 outer layers of rather thick-walled cells forming an ill-defined stereome over the 2--4 layers of larger inner thin-walled cells without a central strand; axillary hairs 2--3 celled, to 100 \um with one basal brown cell, not offset from leaf insertion; rhizoids red-brown, 6--8 \um, smooth, inserted on stem immediately below abaxial costal insertion. Leaves to 1 mm, 2--3.5:1, not plicate, broadest near base, sometimes contracted at the middle into a ligulate distal portion, rounded to obtuse at apex, imbricate when dry and little changed when moist; laterally inserted leaves asymmetric with their postical margins broadly incurved at base; margins at base somewhat cordate but not decurrent, serrulate to serrate above the middle, sometimes serrulate throughout; median cells smooth, 6--9 \um wide, 2--5:1, thick-walled with lumen/wall ratio to 1: 1, but not pitted; alar cells quadrate to transversely elongate in a group up to 10 cells in each dimension, thick-walled, grading into laminal cells; apical cells rhomboidal, nearly isodiametric; costa extending ca.1/2--3/4, often forked distally. Sexual condition dioicous; male plants smaller than females, perigonia on main axis or terminal on short lateral branches; perichaetia on main axis, to 3 mm in an acicular cluster, strongly convolute around the seta, perichaetial bracts ecostate or with a narrow costa present only near mid leaf, abruptly acuminate from a ligulate-lanceolate base, cells long-rectangular, to 12:1. Seta 5--10 mm, short-exserted. Capsule brown, curved and inclined, not distorted or sulcate when dry, somewhat strangulate; urn to 1.8 mm, about 2--3:1; exothecial cells 1--3:1, 12--18 \um wide, thick-walled with a lumen/wall ratio about 3:1; stomata restricted to neck; operculum short-rostrate, about 1/2 as long as urn; exostome horizontally striate basally, becoming low-papillose distally, red-brown; endostome segments lightly papillose, open on keel, narrow, nearly as long as exostome with basal membrane about 1/4 of total length; cilia 2, well-developed. Spores low-papillose, 12--15 µm.
Capsules rare, mature spring. Broad-leaved trees, rock; 200--1000 m; B.C.; Calif., Oreg., Wash.
Bryolawtonia vancouveriensis is a plant mostly epiphytic on broad-leaved trees but also on moist rock. In northern parts of its range deciduous angiosperms such as Alnus are its major phorophytes . To the south, it is especially abundant on the burls of Umbellularia. It reaches its southern limits in Monterey County, California and can reliably be expected in nearly any moist coastal valley from the Bay Area of California to central coastal British Columbia. A form of Bryolawtonia vancouveriensis has been called Bestia occidentalis (Kindberg) Grout. This is very different in leaf arrangement (erect and pressed to stem); in leaf shape (broadest at the base and approaching acute at the apex); and branching pattern (clustered near the top of the decumbent axis). It is immediately recognizable. Nearly all the plants of this morphology are found in coastal British Columbia and Washington. I have found, however, too many intergradations in this form throughout the range of Bryolawtonia vancouveriensis, and deem it unworthy of species recognition.