81. Vulpia C.C. Gmel. (annual fescue)
(Lonard and Gould, 1974)
Plants annual, forming tufts. Flowering stems usually erect.
Leaf sheaths open to the base, the ligule short (less than 1 mm long), truncate
and usually minutely uneven on the margin. Leaf blades flat or with the margins
inrolled. Inflorescences narrow panicles with relatively few ascending branches
toward the base, rarely unbranched and racemose, the spikelets loosely or
densely spaced along the branches, but not regularly paired, all similar in
size and appearance and with at least some fertile florets (these usually
cleistogamous [other species open‑flowering elsewhere]). Spikelets
elliptic in outline, flattened, with 3–15 florets, the apical 1–3 florets
usually sterile, the others perfect. Glumes much shorter than the rest of the
spikelet, narrowly lanceolate to linear, sharply pointed at the tip, usually
glabrous, the lower glume slightly to much shorter, 1‑nerved, the upper
glume 3‑nerved (the nerves sometimes faint), sometimes with a short awn
at the tip. Lemmas lanceolate, tapered to a sharp point or awn at the tip,
rounded on the back, 5‑nerved (sometimes faintly so) with the nerves
converging (arched inward) toward the tip, hairy, roughened, or less commonly
glabrous on the back. Paleas about as long as the lemmas, narrowly elliptic,
with 2 teeth at the tip. Stamen 1(2), this usually remaining enclosed in the
spikelet at maturity, the anthers yellow. Fruits narrowly elliptic to linear in
outline, slightly flattened to circular in cross‑section, reddish brown,
shiny. Twenty‑six species, North America, South America, Europe, Asia, Africa.
Vulpia is often treated as a section or subgenus of the genus Festuca,
but it may be more closely related to Lolium (Tucker, 1996). It differs
from both of these genera in its annual habit and single stamen per floret. The
species of Vulpia are quite variable morphologically and can be
difficult to distinguish. In the descriptions below, lemmas “roughened” refers
to lemmas with minute, stiff hairs, whereas lemmas “hairy” indicates lemmas
with longer, softer hairs. As in other genera of grasses, roughened surfaces
have hairlike structures so small that they generally appear as small teeth or
protrusions, rather than as distinct hairs, even with magnification.