H2 GRAMINEAE. 



12. PANICUM L. Sp. PI. 55- 1753- 



Annuals or perennials of various habit, foliage and inflorescence. Spikelets i-2-flow- 

 ered, when 2-flowered the lower one statninate only. Scales 4, the 3 lower membranous, 

 empty, or the third with a stamiuate flower, varying in the same species; the inner or four " 

 scale chartaceous, shining, enclosing a palet of similar texture and a perfect flower. Awns 

 none, except in Nos. I and 2. Stamens 3. Styles distinct. Stigmas plumose. Grain fre 

 enclosed in the hardened fruiting scale and palet. [Old Latin name for some grass, prot 

 ably the cultivated Sorghum, referring to its panicle, taken from Pliny.] 



About y>o 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 1 

 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, i. P. Crus-galli. 

 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 \y 4 " long. 3. P. digitarioid.es. 



Spikelets oval or obovoid, obtuse, turgid, about i l A" long. 4. P. obtusuni. 



Panicle ovoid or oblong; primary branches spreading or ascending, secondary generally appresset 



occasionally divaricate, bearing numerous pointed spikelets not exceeding i l A" 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 i l A" long, curved. 6. P. rostratum. 



Spikelets less than i l A" long, straight or but slightly curved. 



Culms stout; lateral panicles numerous; ligule short, naked or sparsely short-ciliate. 

 Spikelets about K" long, acute; secondary branches of mature panicle generally 



appressed. 7. P. agrostidiforme. 



Spikelets about iK" 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 



i" 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 i" long. 



Leaves erect or ascending, 2'-^.' long; sheaths generally shorter than the inter- 

 nodes. 10. P. sphaerocarpon. 

 Leaves widely spreading, 5' -8' long; sheaths longer than the internodes. 



ii. P. microcarpon. 

 Spikelets i" or more long. 



Sheaths smooth, glabrous or softly pubescent. 



Nodes strongly barbed ; sheaths and leaves generally softly pubescent; spike- 

 lets elliptic, 2"-2M" long. 12. P. Porterianum. 

 Nodes, at least the upper ones, naked ; sheaths glabrous. 



Spikelets about r r long, elliptic. 13. P. coninnitatmu. 



Spikelets i^"-2" long, oval to obovoid; leaves generally ciliate. 



14. P. macrocarpon. 

 Sheaths papillose -hispid; spikelets about iK" long; panicle generally much 



included, sometimes long-exserted. 15. P. clandestine m. 



Culm leaves lanceolate, rounded, truncate or subcordate at base, sometimes narrowed. 

 Spikelets i'A"-2" long. 



Panicle linear, loose; branches appressed. 16. P. xanthophvsum. 



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. 



1 8. P. Wilcoxianttm. 

 Spikelets less than iK" 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. laxiflonnn. 



Culm leaves generally numerous, usually spreading; culms simple early in the 



season, later profusely branched. 



Spikelets about 1 A" long. 21. P. nilidum. 



Spikelets about i" long. 

 Sheaths glabrous. 



Nodes naked, or the lower sometimes sparingly barbed ; spikelets about 



1 . >"K- "22. P. dichotomum. 



Nodes barbed; spikelets about X" long. 23. P. barbulatum. 



Sheaths pubescent. 



Primary panicle 3' -6' long; spikelets fully i" long, primary culm leaves 

 4-7 long. 24. P. visciditi. 



mary panicle 3 or less long; spikelets hardly i" long; primary culm 

 r , ,. , , * !< -ss than 4' long. 25. P. pubescent. " 



s long an<l very narrow, sometimes involute 



rl.Migat. .1. crowded at base, half as long as or equalling the culm; secondary 

 panicles bome 00 short basal branches. 26 p. depaupcratum. ' 



d narrow, distributed along the culms, which are profusely branched 

 above late in the season. 27 . /. angnst'ifoliu ,. 



