BFNA Title: Rhizogoniaceae
XXX. RHIZOGONIACEAE Brotherus
Steven P. Churchill
Plants small to large, in loose to dense tufts. Stems erect or curved, few branched; central strand well developed; radiculose, often densely tomentose. Leaves spirally arranged or appearing 2-ranked, distant or rather crowded, ovate to narrowly or broadly oblong-lanceolate to linear-lanceolate, apex acute to acuminate, base decurrent or not; margins plane or reflexed to recurved, crenulate, dentate or sharply serrate, teeth single and margins 1-stratose or double and margins 2-stratose; 1-costate, strong, percurrent to short-excurrent, toothed abaxially distally or smooth; laminal cells mostly isodiametric and smooth or bulging mammillose, walls firm and entire; alar region undifferentiated. Specialized asexual reproduction lacking or present, in leaf axils of distal stems and branches, cylindrical. Sexual condition: synoicous, autoicous, or dioicous. Perigonia bud-like, usually below perichaetia. Perichaetia lateral, at base or at mid stem, leaves small and differentiated. Seta elongate, smooth. Capsule horizontal to erect, short to long-cylindrical, symmetric to asymmetric, curved or straight; opercula conic, short to long-rostrate, oblique; peristome double or absent, exostome teeth 16, cross-striate proximally, papillose distally or papillose throughout; endostome basal membrane moderately high, segments 16, keeled, perforate, cilia usually present, 2--3. Calyptra cucullate. Spores spherical, lightly papillose.
Genera 8, ca. 40 species (1 genus, 1 species in the flora): tropical to subtropical with a distinct circum-southern temperate element.
The distinguishing feature of the Rhizogoniaceae is the position of the sporophytes, occurring in the basal half or at the base of the erect stems. For the purpose of this treatment a somewhat traditional circumscription of the Rhizogoniaceae has been maintained. The family has been re-analyzed by T. Koponen (1988). This new view of the family may represent a monophyletic group. The cladogram, however, is not well corroborated and further investigation is needed; under that classification Pyrrhobryum would be placed in the Mniaceae.
SELECTED REFERENCES Inoue, S. and Z. Iwatsuki. 1976. A cytotaxonomic study of the genus Rhizogonium Brid. (Musci). J. Hattori Bot. Lab. 41: 389--403. Koponen, T. 1988. The phylogeny and classification of Mniaceae and Rhizogoniaceae (Musci). J. Hattori Bot. Lab. 64: 37--46. Manuel, G. 1980. Miscellanea Bryologica II. Classification of Rhizogonium Brid., Penzigiella Hookeri Gangulee, and some nomina nuda. Cryptog., Bryol. Lichénol. 1: 67--72.
1. PYRRHOBRYUM Mitten, J. Linn. Soc., Bot. 10: 174. 1868 * [Greek pyrrho, flame-colored, tawny, red, yellowish-red, and bryon, moss]
Stems with exterior 2--3 rows of cells small, thick-walled, interior cells larger, moderately thick-walled; rhizoids often forming a dense tomentum below. Leaves distant [to crowded], linear-lanceolate [to broadly lanceolate], margin doubly-serrate to near base, apex acuminate; costa abaxially toothed [or smooth], transverse section with stereid cells well developed on both side of guide cells; juxtacostal basal cells often weakly differentiated, enlarged, short to rather long-rectangular, lax or not; medial and distal laminal cells uniform throughout, cells isodiametric, rounded to 4--6 sided, thick-walled, smooth; marginal laminal cells 2-stratose. Seta wiry. Capsule inclined to horizontal, usually curved, cylindric, becoming striate and flared at the mouth when deoperculate; exothecial cells quadrate- to rectangular-rounded, moderately thick-walled, somewhat weakly collenchymatous at base; stomates few at base, superficial.
Species 10 (1 in the flora): pantropical and south temperate areas.
The genus is characterized by the elongate stems, distal and spirally arranged broadly to narrowly lanceolate or linear-lanceolate leaves, doubly toothed, 2-stratose leaf margins, costa distally toothed abaxially, mostly isodiametric laminal cells alike to near base, and sporophyte positioned somewhat midway on stem or at the base.
SELECTED REFERENCE. Frahm, J.-P., K. Rembold, T. Röver and T. Schamell. 2003. Synopsis der Gattung Pyrrhobryum (Musci, Rhizogoniaceae). Trop. Bryol. 24: 115--127.
1. Pyrrhobryum spiniforme (Hedwig) Mitten, J. Linn. Soc., Bot. 10: 174. 1868
Hypnum spiniforme Hedwig, Sp. Musc. Frond. 236. 1801; Mnium spiniforme (Hedwig) J. K. A. Müller; Rhizogonium spiniforme (Hedwig) Bruch
Plants often appearing feathery, in loose tufts, dark green and glossy, occasionally yellowish green or brown with age. Stems erect, sometimes curved or curled, to 6 cm or more, solitary or occasionally branched, often grooved below; densely tomentose at base (to ca. 5 mm from base), rhizoids dark rusty-red, papillose. Leaves distant on stem, crispate and curled when dry, erect-spreading to wide-spreading when wet, linear to linear-subulate, (5--)6--8 ´ 0.40--0.75 mm, somewhat concave or folded, apex often terminating in a double tooth, base undifferentiated or occasionally indistinctly decurrent; margins plane, slightly recurved at base, in transverse section 2-stratose, 1-stratose at base; laminal cells uniformly subquadrate to short-rectangular, (7--)10--14 µm; marginal basal cells quadrate to rectangular, 14--30 ´ 10 µm. Seta pale yellowish orange or straw-colored, 4--6 cm. Capsule ellipsoid-cylindric, (1.5--)2--3 mm, neck short; exothecial cells hexagonal, thick-walled; stomata several at urn base and neck; operculum 1.5--2 mm, oblique; exostome teeth reddish orange basally, pale yellow or hyaline distally, endostome segments pale yellow or hyaline, lightly papillose. Calyptra ca. 3.5 mm. Spores 16--18 µm.
Capsules mature Dec.--Apr. Forest, base of tree trunks, logs, soil; Ala., Fla., Ga., La., Miss.; Mexico; West Indies; Central America; South America; Asia; Africa; Pacific Islands; Australia.
This species is characteristic of the southeastern U.S.A. coastal region.