10a. var. dichotomum
Pl. 164 i,
j
P. dichotomum var. barbulatum (Michx.) A.W. Wood
Main stems with the nodes glabrous or
bearded with spreading to downwardly pointed hairs. Leaf
sheaths glabrous or the lowermost sparsely to moderately hairy. Leaf
blades relatively narrow, those of the leaves toward the middle of the main
stem 3–7 mm wide, usually broadest above the base and narrowed somewhat from
below the middle, glabrous or the lowermost moderately hairy. Spikelets 1.8–2.3
mm long, rounded at the tip, glabrous or hairy. 2n=18. May–September (vernal), July–November (autumnal).
Common in the Ozark, Ozark Border,
and Mississippi Lowlands Divisions, uncommon elsewhere in the state (eastern U.S. and adjacent Canada
west to Minnesota and Texas;
Mexico). Mesic to dry upland forests, ledges
of bluffs, and glades, often on rocky slopes; less commonly acid seeps, fens,
and margins of ponds and lakes; also old fields, roadsides, railroads, and
open, dry, disturbed areas.
A recent collection from Carter County
represents a putative hybrid between the morphologically dissimilar P.
dichotomum and P. linearifolium. The specimen originated from a
mixed population of the potential parents in an open, dry, upland forest on a
south‑facing cherty slope. It has the flowering stems with relatively
long, narrow (2.0–4.5 mm wide, more than 20 times as long as wide) leaf blades
and inflorescences with ascending branches, as in P. linearifolium, but
bearded nodes and relatively small spikelets, as in P. dichotomum. The
basal leaves are irregular in length, but relatively narrow, and the leaves of
the flowering stems are irregularly and widely spaced and not clustered near
the base. The spikelets are not mature enough to have produced fruits and
examination of the stamens has been inconclusive, so whether the plants are
sterile cannot be determined. Shinners (1944) and Lelong (1965) have discussed
the occasional appearance of apparently sterile plants of intermediate
morphology in mixed populations of morphologically dissimilar species of Panicum
subgenus Dichanthelium. Further hybrids are to be expected uncommonly in
Missouri.