BFNA Title: Donrichardsia
BRACHYTHECIACEAE -- Donrichardsia
Michael S. Ignatov
Plants medium-sized to robust, rigid, terete to homomallous, in dense to loose mats, green or yellowish, dark, or brownish green, not or slightly glossy. Stems prostrate, occasionally curved at end, with central strand, densely to moderately densely, irregularly loosely branched, branches prostrate to ascending; axillary hairs 2--4-celled, colored throughout. Stem leaves erect-appressed to erect-spreading, broadly ovate to ovate-oblong, broadly acute, sometimes abruptly cuspidate or shortly apiculate; concave, shallowly longitudinally plicate; margin serrulate to serrate throughout, with small acute or blunt teeth; costa strong, wide, 1/12--1/2\x leaf width, short-excurrent, percurrent, or ending at 0.8--0.95\x leaf length; basal cells ovate-rectangular, short, thick-walled, basal cells adjacent to decurrencies somewhat enlarged and forming an indistinct group, or almost undifferentiated from adjacent cells; mid leaf cells 1-stratose or partly 2--4-stratose, elongate to linear, moderately thick-walled. Branch leaves slightly differentiated, usually narrower and having longer mid leaf cells; juvenile branch leaves obtuse to acute. Sexual condition dioicous; perichaetial leaves with slightly reflexed acumina. [Seta red-brown, rough. Capsule red-brown, inclined to horizontal, curved; annulus separating as fragments; operculum rostrate; peristome xerocastique, perfect. Spores small. Calyptra unknown.]
Species: 4 (2
in the flora): e North America, e Asia,
contrasting opinions on the systematic position of Donrichardsia. According to M.
Ignatov and S. Huttunen (2002) and S. Huttunen et al. (2007), however, it includes aquatic
species closely related to and possibly derived from Oxyrrhynchium. Sporophytes have not been found in
Selected references: Crum, H. and L. E. Anderson 1979. Donrichardsia, a new genus of Amblystegiaceae (Musci).
Fieldiana: Botany, New Series. 1: 1--8. Crum, H. and L.
E. Anderson 1981. Mosses of
1. Costa 1/5--1/2\x lamina width; lamina partly 2- to multistratose . . 1. Donrichardsia macroneuron
1. Costa 1/7--1/15\x lamina width; lamina 1-stratose . . 2. Donrichardsia pringlei
1. Donrichardsia macroneuron (Grout) H.A. Crum & L.E. Anderson, Fieldiana, Bot., n.s. 1: 7. 1979
Stems 5--14 cm, branches to 1 cm. Stem leaves 0.9--1.5(--1.8) x 0.4--0.8 mm; ovate-oblong, plicate; costa 1/5-1/2\x laminal width, excurrent, percurrent or ending 3--6 cells before apex, sometimes laterally spurred; basal cells 7--10 \um wide; basal cells adjacent \um,to decurrency almost undifferentiated; mid-leaf cells 30--65 x 6--9 somewhat flexuose. Branch leaves 1--1.5 x 0.15--0.8 mm. Sporophytes unknown.
shallowly submerged in water of calcareous springs at base of limestone slope
in narrow canyons; 570 m;
Donrichardsia macroneuron is known only from Seven Hundred Springs, Edwards County, Texas. The station was described in detail by R. Wyatt and A. Stoneburner (1980), who tried to find more localities in similar habitats nearby, but without success. Plants of Donrichardsia macroneuron have a very broad costa reminiscent of that of Hygroamblystegium noterophilum. The latter species has short, oblong-rhomboidal cells that are never linear and flexuose. In dubious cases, the juvenile leaves around the branch primordia can be examined (see description of the family Brachytheciaceae).
2. Donrichardsia pringlei (Cardot) Huttunen & Ignatov, Syst. Assoc. Special Vol. 71: 138, fig. 142. 2007
Stems to 3--10 cm, branches to 0.4--1.2 cm. Stem leaves 0.7--1.4 x 0.5--0.8 mm; costa stout, but less than 1/10\x leaf width, reaching 0.85--0.95\x leaf length, smooth or ending in an indistinct spine; basal cells near costa ca. 10 \um wide; basal cells adjacent to \um.decurrency 12--20 x 10--15 \um; mid-leaf cells (25--)40--60(--80) x 5--7 Branch leaves 0.7--1.1 x 0.4--0.7 mm. Sporophytes unknown.
in streams and creeks; 300--650(--1950) m elev.;
From the previous assignments, Donrichardsia pringlei is superficially similar to Oxyrrhynchium hians and Rhynchostegium, particularly to R. aquaticum. The last species is autoicous, and if sporophytes are present, it is immediately distinguished by a smooth seta. When sterile, R. aquaticum is also not difficult to distinguish from D. pringlei as the costa usually reaches 0.7--0.85\x leaf length and lacks a spine (or it is indistinct); whereas, the costa of D. pringlei is 0.85--0.95\x leaf length and, if not subpercurrent, it ends in an indistinct spine. Oxyrrhynchium hians is mainly a terrestrial plant, also having a shorter costa but its costa ends in a prominent spine, at least in the branch leaves.