BFNA Title: Physcomitrella
Edit Level R Brum +
Funariaceae - Physcomitrella
Physcomitrella Bruch & Schimper, Bryologia Europaea 1: 13 (fasc. 42. Mon. 1.). 1849 * [Latin -ella, diminutive, resembling a small Physcomitrium]
Plants small, to 0.5 mm, green, scattered to gregarious. Stems short, 3--3.5 mm, simple or branched, rhizoids light brown, smooth. Leaves somewhat crisped when dry, erect-spreading when moist, 2--2.5 × 0.6--1 mm, margin serrulate distally, entire proximally; costa single; cells thin-walled, smooth, proximal cells rectangular, distal cells short-rectangular to rhombic with narrow ends. Sexual condition paroicous. Seta erect, to 0.2 mm. Capsule erect, immersed, symmetric, brown, globose and apiculate, apiculus to 0.2 mm, smooth, wrinkled upon aging, to 0.8 mm, annulus none; peristome lacking; exothecial cells very thin-walled, translucent at maturity, irregular in shape; stomata with single guard cell, restricted to base of capsule, superficial. Operculum not differentiated, dehiscence irregular. Calyptra short, to 0.2 mm, covering apiculus of capsule only, smooth. Spores spherical to slightly elliptical, densely papillose to slightly spinulose, light brown.
Species 2 (2 in the flora): North America, c and n
Europe, Asia (
Physcomitrella is distinguished from other species of Funariaceae by the immersed capsule with irregular dehiscence, and the thin-walled, translucent exothecial cells. The generic name implies a resemblance to Physcomitrium, which is named, however, for its large calyptra, unlike that of Physcomitrella.
selected reference Crum, H. A. and L. E. Anderson. 1955.
Bryologist 58: 1--5. Crum, H.
A. and L. E. Anderson. 1981. Mosses of
1. Costa extending to at most 2/3 the length of the leaf………….1. Physcomitrella readeri
1. Costa extending to leaf apex …………………………………..2. Physcomitrella patens
1. Physcomitrella readeri (J. K. A. Müller) I.G. Stone & G.A.M. Scott, J. Bryol. 7: 604. 1973 
Ephemerella readeri J. K. A. Müller, Hedwigia 41: 120. 1902; Physcomitrella californica H.A. Crum & L.E. Anderson; P. patens subsp. californica (H.A. Crum & L.E. Anderson) B.C. Tan; P. patens subsp. readeri (J. K. A. Müller) B.C. Tan
Plants to 4.5 mm. Stems to 3 mm, branching near base. Leaves to 2 × 0.6 mm, ovate-lanceolate, acuminate, margins plane, serrulate in distal 1/3; costa extending 1/2--2/3 of the leaf length, occasionally slightly forked at apex; proximal cells 75--180 × 35--60 µm, distal cells 45--115 × 15--50 µm, marginal cells not differentiated. Calyptra entire at base, often with a single slit extending toward apex. Spores 27--42 µm.
Capsules mature Jan--Apr. Mineral soil (mudflats) in lake banks; low elevations; Calif.; Asia (China, Japan); Pacific Islands (New Zealand); Australia.
This species is distinguished from the sympatric Physcomitrium patens mainly by its
shorter costa. The size of the rostrum has also been given taxonomic
significance, but capsules of P. patens
may also bear an apiculum reaching 0.2 mm. Similarly, the forked costa has
been considered diagnostic of P.
readeri, but this feature is not constant. The status of P. readeri has been repeatedly
debated, but the geographic restriction of plants with short costae to a
circum-Pacific range may justify taxonomic recognition. Physcomitrella readeri grows with P. patens in two localities in
2. Physcomitrella patens (Hedwig) Bruch & Schimper, Bryologia Europaea 1: 13. (fasc. 42. Mon 1) 1849
Phascum patens Hedwig, Sp. Musc. Frond. 20. 1801; Aphanorrhegma patens (Hedwig) Lindberg
Plants to 5 mm. Stems to 3.5 mm. Leaves to 2.5 × 1 mm, lanceolate or ovate-lanceolate to obovate, acuminate, not or weakly concave, margin of lanceolate leaves somewhat reflexed when dry, serrulate in distal 1/3, rarely below leaf median; costa ending near apex; proximal cells 65--135 × 15--45 µm, distal cells 36--66 × 12--27 µm; marginal cells sometimes longer that medial laminal cells, reaching 150 µm. Calyptra entire at base. Spores 21--33 µm.
Capsules mature Aug -- Jan. Early pioneer on wet mineral soil, river banks, fields; low elevations; B.C., Ont., Que.; Calif., Ill., Ind., La., Md., Mich., Minn., Mo., N.Y., Ohio, Oreg., Pa., Va; c and n Europe; Asia (w Siberia).
Physcomitrella patens is fairly variable in leaf shape and stature. The species is similar to Aphanorrhegma, with which it is broadly sympatric but far less common. Physcomitrella patens differs from A. serratum by the thin-walled exothecial cells and the unlobed calyptra.