7. CÉNCHRUS, L. Hedgehog- or Bur-Grass. ([Pl. 14.])
Spikelets as in Panicum, awnless, but enclosed 1 to 5 together in a globular and bristly or spiny involucre, which becomes coriaceous and forms a deciduous hard and rigid bur; the involucres sessile in a terminal spike. Styles united below. (An ancient Greek name of Setaria Italica.)
1. C. tribuloìdes, L. Annual; culms branched and ascending (1° high or less); leaves flat; spike oblong, of 8–20 spherical heads; involucre prickly all over with spreading and barbed short spines, more or less downy, enclosing 2 or 3 spikelets.—Sandy soil, on river banks, etc. Aug.—A vile weed.
8. AMPHICÁRPUM, Kunth. ([Pl. 13.])
Spikelets jointed upon the pedicels, 1-flowered, oblong or ovoid, of two kinds; one kind in a terminal panicle, deciduous from the joint without fruit, although the flower is perfect; the other kind solitary at the extremity of slender runner-like radical peduncles (more or less sheathed toward the base), much larger than the others, perfect and fertile, subterranean, fertilized in the bud. Glumes 3, nearly equal, 5-nerved in the panicle, many nerved in the fertile spikelets; palet a little shorter; all becoming indurated and enclosing the very large grain. Stamens 3 (small in the radical flowers). Stigmas plumose, deep purple. (Name from ἀμφίκαρπος, doubly fruit-bearing.)
1. A. Púrshii, Kunth. Annual or biennial(?), erect, 1–4° high; leaves lanceolate, copious on the lower part of the culm, hispid, especially on the sheaths; panicle strict, naked; grain ovoid or oblong (2–3´´ long), terete.—Moist sandy pine-barrens, N. J. to Fla. Sept.
9. LEÉRSIA, Swartz. White Grass. ([Pl. 7.])
Flowers crowded in one-sided panicled spikes or racemes, perfect, but those in the open panicles usually sterile by the abortion of the ovary, those enclosed in the sheaths of the leaves close-fertilized in the bud and prolific. Spikelets 1-flowered, flat, more or less imbricated over each other, jointed upon the short pedicels. Glumes 2, chartaceous, strongly flattened laterally or conduplicate, awnless, bristly-ciliate on the keels, closed, nearly equal in length, but the lower much broader, enclosing the flat grain. Palet none. Stamens 1–6. Stigmas feathery, the hairs branching.—Perennial marsh grasses; the flat leaves, sheaths, etc., rough upward, being clothed with very minute hooked prickles. (Named after John Daniel Leers, a German botanist.)
[*] Spikelets narrowly oblong, rather loosely crowded.
1. L. Virgínica, Willd. (White Grass.) Panicle simple; the spikelets closely appressed on the slender branches, around which they are partly curved (1½´´ long); stamens 2 (a third imperfect or wanting); glumes sparingly ciliate (greenish-white).—Wet woods; Maine to Minn., and southward. Aug.