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.
