II2 GRAMINEAE. 
12. PANICUM L. SD: cela Sse e753: 
Annuals or perennials of various habit, foliage and inflorescence. Spikelets 1-2-flow- 
ered, when 2-flowered the lower one staminate only. Scales 4, the 3 lower membranous, 
empty, or the third with a staminate flower, varying in the same species; the inner or fourth 
scale chartaceous, shining, enclosing a palct of similar texture and a perfect flower. Awns 
none, except in Nos. rand 2, Stamens 3. Styles distinct. Stigmas plumose. Grain free, 
enclosed in the hardened fruiting scale and palet. [Old Latin name for some grass, prob- 
ably the cultivated Sorghum, referring to its panicle, taken from Pliny. } 
About 300 species, in temperate and tropical regions. The geographic distribution of many of 
our species is not well ascertained. The old English name Panic or Panic-grass, is often applied 
to any of the species. 
Panicle oblong to ovoid; spike-like branches sessile, more or less spreading; spikelets in 2-4 rows, 
secund; third scale, and sometimes the second and first, awn-pointed or awned. 
Sheaths smooth; culms 2°-4° tall; fourth scale ovate, abruptly pointed. 1. P. Crus-gall7. 
Sheaths, at least the lower ones, hirsute; culms 4°-6° tall; fourth scale ovate-lanceolate, 
acuminate. 2. P. Walteri. 
Panicle linear, spicate at summit; branches appressed, sessile; third scale merely acute or acuminate. 
Spikelets ovate, acute, about 14’ long. 3. P. digitarioides. 
Spikelets oval or obovoid, obtuse, turgid, about 1's"’ long. 4. P. obtusum. 
Panicle ovoid or oblong; primary branches spreading or ascending, secondary generally appressed, 
occasionally divaricate, bearing numerous pointed spikelets not exceeding 1'2"' in length. 
Palet in the axil of the third scale conspicuous, enlarged, much exceeding the fourth scale; 
spikelets open. 5. P. hians. 
Palet in the axil of the third scale inconspicuous; spikelets closed. 
Spikelets 1!'’ long, curved. 6. P. rostratum., 
Spikelets less than 1%’ long, straight or but slightly curved. 
Culms stout; lateral panicles numerous; ligule short, naked or sparsely short-ciliate. 
Spikelets about %'’ long, acute; secondary branches of mature panicle generally 
appressed. 7. P. agrostidiforme. 
Spikelets about 14%'’ long, acuminate; secondary branches of the mature panicle 
generally spreading or divaricate. 8. P. elongatum. 
Culms slender, simple, or occasionally with a single lateral panicle; spikelets about 
1’ long, acuminate; ligule short, pilose. 9. P. longifolium. 
Branches of the panicle single, in pairs or fascicled, simple or subdivided, naked below; spikelets 
on slender pedicels. 
Basal leaves, or those near the base, much shorter and broader than the upper culm leaves; 
spikelets turgid, obtuse or acutish; panicle not over 6’ in length, generally much smaller. 
Culm leaves broad, cordate and clasping at base. 
Spikelets less than 1’’ long. 
Leaves erect or ascending, 2'-4’ long; sheaths generally shorter than the inter- 
nodes. 10. P. sphaerocarpon. 
Leaves widely spreading, 5'-8’ long; sheaths longer than the internodes. 
‘ 11. P. microcarpon. 
Spikelets 1'’ or more long. 
Sheaths smooth, glabrous or softly pubescent. 
Nodes strongly barbed; sheaths and leaves generally softly pubescent; spike- 
lets elliptic, 2'’-2's'’ long. 12. P. Porterianum. 
Nodes, at least the upper ones, naked; sheaths glabrous. 
Spikelets about 1’ long, elliptic. 13. P. commutatum. 
Spikelets 114'’-2"' long, oval to obovoid; leaves generally ciliate. 
14. P. macrocarpon. 
Sheaths papillose-hispid; spikelets about 1%’ long; panicle generally much 
included, sometimes long—exserted. 15. P. clandestinum, 
Culm leaves lanceolate, rounded, truncate or subcordate at base, sometimes narrowed. 
Spikelets 114'’-2"’ long. 
Panicle linear, loose; branches appressed. 16. P. xanthophysum. 
Panicle ovoid to oblong, compact; branches more or less spreading. 
Leaves spreading, 3'’-6'’ wide; spikelets obovoid. 17. P. Scribnerianum. 
Leaves erect, less than 2'’ wide, long-acuminate; spikelets elliptic. 
18. P. Wilcoxianum. 
Spikelets less than 1!s"’ long. 
Culm leaves 1-4, erect; culms mostly simple, never profusely branched late in the 
season. 
Sheaths and leaves glabrous. 19. P. boreale. 
Sheaths and leaves pubescent. 20. P. laxiflorum. 
Culm leaves generally numerous, usually spreading; culms simple early in the 
season, later profusely branched. 
Spikelets about '%"’ long. a1. P. nitidum. 
Spikelets about 1’’ long. 
Sheaths glabrous. 
Nodes naked, or the lower sometimes sparingly barbed; spikelets about 
1’ long. 22. P. dichotomum. 
Nodes barbed; spikelets about 4"’ long. 23. P. barbulatum., 
Sheaths pubescent. 
Primary panicle 3'-6' long; spikelets fully 1'’ long, primary culm leaves 
4'-7' long. 24. P. viscidum., 
Primary panicle 3’ or less long; spikelets hardly 1'’ long; primary culm 
leaves less than 4’ long. 25. P. pubescens. 
Culm leaves long and very marrow, sometimes involute. 
Leaves elongated, crowded at base, half as long as or equalling the culm; secondary 
panicles borne on short basal branches. 26. P. depauperatum. 
Leaves long and narrow, distributed along the culms, which are profusely branched 
above late in the season. 27. P. angustifolium, 
