BFNA Title: Donnellia
XX. DONNELLIA Austin, Bull. Torrey Bot. Club 7: 15. 1880 * [for John Donnell Smith, 1829--1928]
William R. Buck
Leaves erect to erect-spreading, sometimes homomallous when dry, oblong-lanceolate to lanceolate-ovate, gradually short-acuminate, concave; distal cells long-rhomboidal to long-hexagonal, smooth; alar cells enlarged, thick-walled, colored in 1--3 rows, scarcely inflated. Sexual condition autoicous. Seta short, smooth. Capsule erect to suberect, small, short-cylindric, slightly or not contracted below the mouth; exothecial cells somewhat collenchymatous; annulus none; peristome double, pale, exostome teeth on exterior surface with straight center line, not furrowed, smooth (not cross-striolate), scarcely projecting at back; endostome with very low or absent basal membrane, segments linear, ± keeled, not perforate, finely papillose, almost as long as the teeth, sometimes fugaceous, cilia none. Spores large.
Species 5 (1 in the flora): most common in tropical America, but also extending into tropical Africa; North America, Central America, n South America, c Africa.
SELECTED REFERENCES Buck, W. R. 1988. Donnellia (Sematophyllaceae) resurrected and refound in Florida after 110 years. Bryologist 91: 134--135. Buck, W. R. 1994. A synopsis of the American species of Donnellia (Sematophyllaceae). Hikobia 11: 377--385.
1. Donnellia commutata (J. F. K. Müller) W. R. Buck, Bryologist 91: 134. 1988
Neckera commutata J. F. K. Müller, Bot. Zeit. 15: 385. 1857; Donnellia floridana Austin, illegitimate name; Fabronia donnellii Austin; Meiotheciopsis commutata (J. F. K. Müller) W. R. Buck; Meiothecium tenerum Mitten
Stems irregularly branched, the branches ascending. Leaves homomallous, lanceolate, 0.6--1.1 ´ 0.19--0.36 mm, only slightly concave; margins entire; cells thick-walled and long-rhomboidal throughout; alar cells shortly oblong, thick-walled, yellow, slightly inflated, in a single row, those directly above not inflated or colored, quadrate. Seta 2.5--3.5 mm. Capsule 0.7--1.2 mm; peristome bone white when dry, ± translucent when moist, exostome teeth with conspicuous lamellae on front surface; endostome fragile, appearing lacking in deoperculate capsules.
Capsules mature winter. White-sand evergreen oak scrub forests, mostly growing on trunks and large branches (including those in the canopy) of Quercus spp.; low elevations; nc Fla.; Mexico to southern Brazil; Greater Antilles.
This species is not uncommon in oak scrubs of north-central Florida, but has been mostly overlooked because of its sympatry with and morphological similarity to Sematophyllum adnatum, one of the great weedy mosses. Donnellia commutata may be distinguished satisfactorily only when fertile by its shorter setae, white peristome (when dry), and ± smooth exostome teeth. The endostome often appears absent because the segments break off shortly after the loss of the opercula. However, they can be easily demonstrated by the dissection of mature, operculate capsules.