1. Lorentziella imbricata (Mitten) Brotherus in H. G. A. Engler and K. Prantl, Nat. Pflanzenfam. 216 [I,3]: 511. 1903.
Leptangium imbricatum Mitten, J. Linn. Soc., Bot. 12: 240. 1869; Acaulon runyonii 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 paroecious 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 an imperfectly divided single, 2-nucleate guard cell. Calyptra narrowly conic, covering tip of capsule. Spores of 2 sizes: large, faintly granulose, yellow-brown, 120-160 µm, and small, densely granular, shriveled, 32-73 µm.
Capsules mature winter. Often found in loose soil at granitic outcrop margins in association with Selaginella; low to moderate elevations; Tex.; South America (Argentina, Paraguay, Uruguay).
Lorentziella imbricata is known from Bastrop, Brazos, Burnet, Cameron, Gillespie, Llano, and Travis counties in central Texas. It 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, 2-nucleate with a central opening.