keys to the vascular plants of east texas - Botanical Research ...

852 POACEAE/BRACHYELYTRUM
(e.g., Stephenson ined.) treating all three taxa as parts of a single species and others considering
them worthy of recognition as separate species (Stephenson 1971; Tucker 1988; Kartesz 1999).
We are following a recent revision of the genus (Saarela et al. 2003), based on morphological
and molecular data, in recognizing the variation at the specific level.
The disjunct e Asia–e North America distribution pattern exhibited by this and other genera has complex
origins and is of interest to plant geographers. In the geologic past, dispersal between the Eurasian and
North American continents was possible across both the Bering and North Atlantic land bridges, and the
combined area is considered a single “Holarctic” biogeographic region. The fossil record shows that many
plants had extensive distributions across the Northern Hemisphere—for example, temperate forests with
tropical elements occurred very broadly and reached their maximum extension in the mid-Tertiary (the
Tertiary extended from 65 million years ago to 1.8 mya). This widespread flora has been referred to as the
Arcto-Tertiary flora, the Tertiaro-mesophytic flora, the boreotropical flora, or a mixed mesophytic forest.
Geohistorical events from the mid-Tertiary to the present have included alterations in the shapes of the
northern land masses, fluctuations in sea levels, plate tectonic movements, mountain building, glaciation,
and other changes in the climate. As a result, there have been great changes in both the composition and
the disposition of the flora, and the ranges of many plants have been greatly restricted (e.g., eliminated
from Europe and w North America). A significant number of plants that were once much more widespread
now survive in only two areas, e North America and e Asia. Though this disjunct distribution pattern
has complex and multiple origins, with similar present day distributions differing in time and manner
of origin, the consensus is that the e Asia–e North America pattern is in general a relict of the
maximum development of Northern Hemisphere temperate forests (with tropical elements) in the Tertiary,
with greater survival in e Asia and e North America and higher rates of extinction in Europe and w
North America. According to Wen (1999), ca. 65 genera of seed plants have this disjunct distribution. The
genus Brachyelytrum is an example (other East TX examples include, but are not limited to, Aletris,
Ampelopsis, Apios, Campsis, Carya, Diarrhena, Halesia, Hamamelis, Lindera, Ly onia, Menispermum, Nyssa,
Parthenocissus, Penthorum, Phryma, Podophyllum, Sassafras, Saururus, Stewartia, Tipularia, Trachelospermum,
Triosteum, and Zizania) (Li 1952; Little 1970; Graham 1972; Boufford & Spongberg 1983; Hamilton
1983; Hsü 1983; Wu 1983; Ying 1983; Tiffney 1985a, 1985b; Cox & Moore 1993; Graham 1993a, 1999;
Xiang et al. 1998; Wen 1999, 2001; Dilcher 2000; Donoghue et al. 2001; Xiang & Soltis 2001).
This genus has been variously thought to be in either the Pooideae (Festucoideae) (e.g., Hitchcock
1951) or Bambusoideae (e.g., Campbell et al. 1986; Tucker 1988), but recent evidence confirms
its place in the Pooideae (Grass Phylogeny Working Group 2001). (Greek: brachys, short,
and elytron, cover, husk, sheath, presumably in reference to the small glumes) (subfamily
Pooideae, tribe Brachyelytreae)
REFERENCES: Babel 1943; Koyama & Kawano 1964; Stephenson 1971, ined.; Macfarlane & Watson
1980; Nixon et al. 1980a; Campbell 1983b; Campbell et al. 1986; Tucker 1988; Saarela et al. 2003.
Brachyelytrum erectum (Schreb.) P. Beauv., (upright), BEARDED SHORT HUSK, LONG-AWNED WOOD
GRASS. Perennial with short knotty rhizomes; culms 50–90(–100) cm tall, erect to ascending,
usually with retrorse pubescence near the nodes; leaves cauline, 2–6; ligule a scale 1–3.5 mm
long; leaf blades 8–17.5 cm long, 5–20 mm wide, flat; inflorescence a narrow panicle, often appearing
racemose, 7–17 cm long; spikelets 8–13 mm long (excluding awns), with 1 fertile floret,
disarticulating above the glumes; lower (first) glume absent or rudimentary (� 1 mm long); upper
glume 1–4(–8) mm long; lemma 8–13 mm long, strongly antrorsely hispid, tapering into an
awn 12–25(–30) mm long; palea slightly shorter than lemma; rachilla prolonged beyond palea
as a slender awn-like bristle 5–8 mm long; stamens 3, the anthers ca. 5–6 mm long. Mesic forests,
beech-hardwood slopes; Nacogdoches, Sabine (BRIT), San Augustine, Shelby (TOES 1993),
Polk, Rusk, Tyler (Turner et al. 2003), and Jasper (J. Singhurst, pers. comm.) cos. in the
Pineywoods; se Canada and e U.S. from ME s to FL w to MN and TX. May–Sep. This species was
first reported for TX from Nacogdoches Co. by Nixon et al. (1980a). Vegetatively and in habitat
preference, it superficially resembles two other woodland species, Bromus pubescens and
Chasmanthium latifolium; however, Brachyelytrum can be easily distinguished by its spikelets
with only 1 floret (versus 4–many florets). (TOES 1993: IV) �