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BFNA Title: Donrichardsia |
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BRACHYTHECIACEAE -- Donrichardsia
Plants medium-sized to robust, rigid, in dense
to loose mats, green or dark-, yellowish or brownish green, not or slightly
glossy. Stems prostrate,
occasionally curved apically, with central strand, densely to moderately
densely, terete to homomallous, irregularly loosely branched, branches
prostrate to ascending, rather densely; axillary hairs 2--4-celled, colored
throughout; juvenile branch leaves obtuse to acute. 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 and wide,
1/12 to 1/2 of leaf width, short-excurrent, percurrent, or ending at 0.8--0.95\x
the 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. Sexual condition dioicous; perichaetial leaves with slightly
reflexed acumina. Seta red-brown, rough. Capsule
red-brown, inclined to horizontal, curved; annulus separating by
fragments; operculum rostrate; peristome xerocastique,
perfect. Spores small. Calyptra unknown. Species: 4 (2
in the flora): eastern North America, There are
contrasting opinions on the systematic position of Donrichardsia. However,
according to M. S. Ignatov and S. Huttunen (2002) and S. Huttunen et al.
(2007), it includes aquatic species closely related to and possibly derived
from Oxyrrhynchium. Sporophytes have not been found in SELELECTED REFERENCES Crum, H. and L. E. Anderson. 1979. Donrichardsia, a new genus of Amblystegiaceae (Musci).
Fieldiana: Botany, n. s. 1: 1--8. Crum, H. and L.
E. Anderson 1981. Mosses of 1. Costa
1/5--1/2 of lamina width; lamina partly 2- to multistratose . . 1. Donrichardsia macroneuron 1. Costa
1/7--1/15 of 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 Hygroamblystegium macroneuron Grout, Bryologist 36:
1. 1933; Eurhynchium macroneuron (Grout) H. A. Crum Stems 5--14 cm, branches to 10 mm. Stem
leaves 0.9--1.5(--1.8) x 0.4--0.8 mm; ovate-oblong, plicate; costa
1/5-1/2 laminal width, excurrent, percurrent or ended 3-6 cells before apex,
sometimes laterally spurred; basal cells 7--10 /um wide; basal cells adjacent
to decurrency almost undifferentiated; mid-leaf
cells 30--65 x 6--9 /um, somewhat flexuose. Branch leaves 1--1.5 x 0.15--0.8 mm. Sporophytes unknown. Rocks,
shallowly submerged in water of calcareous springs at base of limestone slope
in narrow canyons; 570 m; The single
known locality of Donrichardsia macroneuron is
Seven Hundred Springs in Edwards County, Texas. This locality was described
in details by R. Wyatt and A. Stoneburner (1980),
who also tried to find more localities in similar habitats nearby, but without
success. Plants of D. macroneuron have very broad costae reminiscent of that
of Hygroamblystegium noterophilum.
The latter species has short, oblong-rhomboidal cells that are never linear and
flexuose, and, in dubious cases, the juvenile
leaves around the branch primordia can be examined (see the description of
the family Brachytheciaceae). 2. Donrichardsia pringlei
(Cardot) Huttunen & Ignatov, Syst. Assoc. Special Vol.
71: 138, 142. 2007 Rhynchostegium pringlei Cardot, Rev.
Bryol. 37: 70. 1910; Eurhynchium pringlei (Cardot) H. A. Crum & L. E. Anderson Stems to 3--10 cm, branches to 4--12 mm. Stem
leaves 0.7--1.4 x 0.5--0.8 mm; costa stout, but less than 1/10 of leaf
width, reaching 0.85-0.95 of leaf length, smooth or ending in an indistinct
spine; basal cells near costa ca. 10 /um wide; basal cells adjacent to decurrency 12--20 x 10--15 /um; mid-leaf cells (25--)40--60(--80) x 5--7 /um. Branch leaves 0.7--1.1 x 0.4--0.7 mm. Sporophytes unknown. Rocks
in streams and creeks; 300--650(--1950) m elev.; As one
may assume from the previous placement of this species, it is superficially
similar to Oxyrrhynchium
hians and Rhynchostegium, particularly to
R. aquaticum.
The latter species is autoicous. If sporophytes are present, it is
immediately distinguished by its smooth seta. When sterile, R. aquaticum is
also not difficult to distinguish from D.
pringlei as the costa usually reaching
0.7--0.85 the leaf length and lacks a abaxial terminal costal spine (or it is
indistinct) whereas the costa of D. pringlei is
0.85--0.95 the 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. |