Piptochaetium stipoides
Piptochaetium avenaceum
purple spear grass, stipoid ricegrass
black-seed spear grass, blackseed needlegrass
20-60 cm, erect to ascending;
nodes 2-4, dark, glabrous.
(30)40-100 cm, glabrous;
nodes 2-3, narrowed, yellowish to reddish.
glabrous or hispidulous towards the collar;
ligules 0.8-2 mm, glabrous, abaxial surfaces scabridulous, margins occasionally ciliate;
blades (5)14-30 cm long, 0.2-0.4 mm wide, linear, glabrous or villous, margins scabridulous.
glabrous;
ligules rounded, sometimes highest at the sides, entire, of basal leaves 0.4-3.3 mm, of upper leaves 1.8-2.5 mm;
blades 8-30 cm long, 0.6-3 mm wide, usually involute and about 0.5 mm in diameter, 3-veined, abaxial surfaces glabrous, smooth, adaxial surfaces scabrous over the veins, margins scabrous.
4-15 cm long, 1.5-3 cm wide, with 10-70 spikelets;
branches ascending, scabridulous;
pedicels 1-11 mm, hispid.
14-22 cm, open, with (10)15-25 spikelets;
branches lax, divergent, spikelets confined to the distal 1/2;
pedicels 15-50 mm, flattened, hispid.
subequal, 4-8.5 mm long, 1.5-2 mm wide, purple towards the base, glabrous, 5-veined, apices aristulate;
florets 2.3-4(5) mm long, 0.8-2.3 mm thick, obovoid, globose to laterally compressed;
calluses 0.5-0.6 mm, blunt, hairs white to golden tan;
lemmas shiny, glabrous, striate, dark brown to black at maturity, wholly smooth to conspicuously verrucose or sharply papillose, at least distally, constricted below the crown;
crowns well-developed, 0.6-1.6 mm wide, distal margins slightly to strongly revolute, inner surfaces densely covered with hooks and hairs;
awns 15-25 mm, eccentric, twice-geniculate, tardily deciduous;
paleas 2.5-5 mm;
lodicules 2, linear;
anthers about 0.5 mm.
subequal, 9-15 mm long, 0.9-1.9 mm wide, acute;
lower glumes 3(5)-veined;
upper glumes 5-veined;
florets 7-13 mm long, 1-1.2 mm thick, terete;
calluses 2-3 mm, sharp, strigose, hairs golden brown at maturity;
lemmas glabrous, tan to brown at maturity, smooth below, sharply tuberculate in the distal 1/3, constricted below the crown;
crowns 0.5-0.6 mm wide, straight, not revolute, hairy, hairs 0.2-0.5 mm, golden brown;
awns 40-75 mm, persistent, twice-geniculate, basal segment hispid, terminal segment scabrous;
paleas 7-14 mm;
anthers 0.3-0.5 mm or 3-4 mm, not penicillate.
1.5-2.5 mm, spherical to ellipsoid.
3.5-6 mm, terete.
& Giussani (2002) mistakenly cited Gould (1958) as having reported 2n = 28.
= unknown.
= 22.
Piptochaetium stipoides
Piptochaetium avenaceum
Piptochaetium stipoides is native to South America. There is one known population in the Flora region, in Marin County, California, which grows with P. setosum in a meadow adjacent to an old dirt road. The origin of the population is not known; it has been suggested that the seeds might have been brought in by birds, as the area was a bird refuge at one time.
The Californian plants belong to Piptochaetium stipoides (Trin. & Rupr.) Hack. var. stipoides, which differs from the only other variety recognized by Cialdella and Arriaga (1998), P. stipoides var. echinulatum Parodi, in having lemmas that are mostly smooth as well as a less revolute crown.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Piptochaetium avenaceum grows in open oak and pine woods, often on sandy soils, throughout most of the coastal plain of the eastern United States, extending north up the Mississippi valley, and also on the east side of Lake Michigan. With the exception of one record from southern Ontario, Canada (collected in 1965 and not seen in Canada since, even though it has been searched for, fide Michael Oldham, pers. comm.), P. avenaceum is known only from the contiguous United States.
Piptochaetium avenaceum is very similar to P. avenacioides, differing only in its smaller size and more widespread distribution. It is also similar to P. leianthum (Hitchc.) Beetle, a species of northeastern Mexico, from which it differs in it larger size. The existence of two ranges of anther length suggests that the species is sometimes cleistogamous.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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