98 * Rhodora [May 
31. Spikelets less than 2 mm. long ‘ : è : 
32. Plant pilose-pubescent throughout with long, spreading white hairs 
30. P. ATLANTICUM 
32. Plant not pilose-pubescent . i i : : ME 
33. Culms glabrous; spikelets 2 mm. long : i . 26. P. WERNERI 
33. Culms puberulent, at least below; spikelets 2.573 mm. long 
23. P. BICKNELLII 
34. Culms appressed-pubescent or puberulent . 33- P. COLUMBIANUM 
34. Culms with spreading pubescence . à . 3 . 35 
35. Leaves, firm and usually rigid; panicle usually purplish, branches 
34 
rather rigid 3 ^ . 1 i ; . 81. P. UNCIPHYLLUM 
35. Leaves thin, with a peculiar lustre; panicle green, rather densely 
flowered, branches capillary and tlexuose 32. P. LANUGINOSUM 
$ I. SYNTHERISMA. 
Spikelets borne in pairs, one sessile and one pedicellate, in: simple, 
slender, one-sided racemes, which are digitate or fasciculate at the 
summit of the culm; glumes four, sometimes three by suppression of 
the first one. 
* Rachis three-angled, not winged. 
1. PANICUM FILIFORME Linn. Sp. Pl. 57. 1753. (Duégitaria 
filiformis Muhl. Descr. 131. 1817 ; Syntherisma filiformis Nash, Bul. 
Torr. Bot. Club, 22: 420. 1395. 
A slender, simple or somewhat branched, annual, r.5 to 7 dm. 
high, with long-exserted panicles of 2 to 5 slender, erect or ascend- 
ing racemes, 2-10 cm. long. Sheaths flattened, keeled, papillose- 
hirsute; ligule a scarious irregularly toothed ring 1-2 mm. long; 
leaf-blades 3-20 cm. long, r-4 mm. wide, erect, usually glabrous on 
the lower surface, the upper surface and margins rough, papillose- 
hirsute at the base. Racemes alternate, the rachis 3-angled, the 
angles hispidulous. Spikelets in pairs, about 1.8 mm. long, elliptic, 
acute, on hispidulous 3-angled pedicels ; first glume obsolete ; second 
glume about three fourths as long as the spikelet, 3-nerved, the 
margins and internerves pubescent with long appressed hairs ; third 
glume slightly shorter than the fourth, 7-nerved, pubescent with ap- 
pressed hairs; flowering glume deep chestnut brown at maturity, 
striate, apiculate. Palea of equal length and similar texture. 
General distribution: in dry sandy soil. Massachusetts to Mich- 
igan, south to North Carolina and Indian Territory. August to Sep- 
tember. . 
MASSACHUSETTS: Waltham, sandy ground, W. P. Rich, Sept. 2, 
1889; Springfield, Maria Z. Owen, Sept. 9, 1885; East Longmeadow, 
W. Deane, Aug. 31, 1895; Norwood, Purgatory swamp, Æ. F. 
