BFNA Title: Gigaspermaceae
Author: A. E. Rushing
Date: December 20, 2005
Edit Level: R Brum+
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden
BFNA Web site: http://www.mobot.org/plantscience/BFNA/bfnamenu.htm

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XX. GIGASPERMACEAE

Ann E. Rushing

Plants minute, with upright branches arising from a pale, fleshy, subterranean, aphyllous stem. Leaves crowded above, broadly concave, ovate, elliptic to obovate, cell walls of lamina often thickened at the corners. Seta short to moderately elongate. Capsule globose, immersed or exserted; gymnostomous; operculum present or absent.

Genera 6 (1 in the flora): largely distributed in the Southern Hemisphere.

The major defining feature of the family is the fleshy, underground stem from which short gametophore branches are produced in abundance. Sporophyte features differentiate the six, mostly monotypic genera, Chamaebryum in South Africa, Costesia in South America, Gigaspermum in Mexico, Australia, New Zealand, and South Africa, Lorentziella in southern U.S.A. and South America, Neosharpiella in Mexico and South America, and Oedipodiella in South Africa.

1. LORENTZIELLA J. K. A. Müller, Linnaea 42: 229. 1879 * [For Paul Günter Lorentz, 1835--1881, German bryologist]

Leaves imbricate distally, concave, broadly ovate to elliptic, abruptly narrowed to a long awn; costa narrow, extending to the base of the awn. Capsule immersed to slightly emergent, base truncate, operculum not differentiated.

Species 1 or 2 (1 in the flora): disjunctive from southern U.S.A. to southern South America.

Lorentziella is a genus of minute, ephemeral mosses comprising one, or at most two, species. The perennial, subterranean stem or rhizome system gives rise to upright, above-ground plants in the late fall and early winter. Above-ground plants are produced in abundance during mild, wet winters but less commonly when conditions are dry. The broadly concave leaves completely surround the globose, cleistocarpous capsules of the immersed sporophytes. The glaucous, blue-green color of the ephemeral, above-ground plants is reminiscent of Bryum argenteum while the cabbage shape of the plants resembles a small Funaria gametophyte prior to elongation of the seta.

SELECTED REFERENCES: Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern North America. Vol. 1. New York. Fife, A. J. 1980. The affinities of Costesia and Neosharpiella and notes on the Gigaspermaceae (Musci). Bryologist 83: 466--476. Lawton, E. 1953. Lorentziella, a moss genus new to North America. Bull. Torrey Bot. Club 80: 279--288. Reese, W. D. 1984. Manual of the Mosses of the Gulf South. Baton Rouge. Rushing, A. E. and J. A. Snider. 1980. Observations on sporophyte development in Lorentziella imbricata (Mitt.) Broth. J. Hattori Bot. Lab. 47: 35--44. Sharp, A. J., H. A. Crum and P. Eckel. 1994. The Moss Flora of Mexico. Part 1. Mem. New York Bot. Gard. 69.

1. Lorentziella imbricata (Mitten) Brotherus in A. Engler & K. Prantl, Natürl. Pflanzenf. 1(3): 511. 1903

Leptangium imbricatum Mitten, J. Linn. Soc. London Bot. 12: 240. 1869; Acaulon runyoni Grout; A. megalosporum Grout

Plants small, bulbiform in shape with distally densely crowded leaves, light green to glaucous, in dense clusters or tufts. Stems above ground erect, 2--5 mm. Leaves 1.5--4 mm; proximal leaves less crowded, ovate with acute tips; margins entire to weakly serrate; distal laminal cells elongate, oblong-hexagonal to short-rhomboidal; proximal laminal cells quadrate to short-rectangular. Sexual condition paroicous with antheridia in naked clusters in axils of distal leaves. Seta short, less than 0.25 mm. Capsule immersed to slightly emergent when mature and fully expanded, pale green, cleistocarpous, globose to ellipsoidal or ovate with a truncate base, 1--1.5 mm long, 1--2 mm in diameter; stomata at base of capsule with a central opening in one guard cell or sometimes imperfectly divided. Spores of two sizes: large, faintly granulose, yellow-brown, 120--160 µm, and small, densely granular, shriveled, 32--73 µm. Calyptra minute, narrowly conic, covering the tip of the capsule, fugacious.

Capsules mature winter. Often found in loose soil at granite outcrop margins in association with Selaginella; known only from a few collections; c Tex. (Bastrop, Brazos, Burnet, Cameron, Gillespie, Llano, and Travis counties); South America (Argentina, Paraguay, Uruguay).

The North America species, Lorentziella imbricata, is named for the closely imbricate distal leaves. In Texas, fertilization and sporophyte growth occur in the winter months and by late spring little trace of the above-ground plants remain. Spores have been described as angular, probably due to packing and space constraints within the capsule. Stomata have been described as having a single guard cell with a central opening or two guard cells. Careful study of guard cells reveals that most are single-celled with a central opening.