GEAMINEAE (GRASS FAMILY) 



153 



157. D. diandra x I. 

 Spikelet and fruit. 



66. DIARRHENA Beauv. 



Spikelets 3-5-flowered, the uppermost florets sterile ; glumes unequal, much 

 shorter than the florets ; lemmas broad, coriaceous, rigid, smooth and shining, 

 convex below, 3-nerved, acuminate or mucronate-pointed ; 

 palea firm, 2-keeled ; stamens 2, rarely 1 ; grain large, usually 

 exceeding the lemma and palea, obliquely ovoid, obtusely 

 beaked, with a shining coriaceous pericarp. Nearly smooth 

 perennials, with simple culms from a creeping rootstock, flat 

 leaves and narrow few-flowered panicles. (Name composed 

 of 5/j, two, and Hfrfav, man, from the two stamens.) 



1. D. diandra (Michx.) Wood. Culms 6-9 dm. high; 

 leaves nearly as long as the culm, 1-1.8 cm. wide; panicle 

 very simple, 1-2.5 dm. long ; spikelets short-pediceled, 10-16 



mm. long. (Festuca Michx.; Korycarpus Ktze. ; D. americana Beauv.) 

 Shaded river banks and woods, 0. to S. Dak., and southw. July, Aug. FIG. 157. 



67. UNiOLA L. SPIKE GRASS 



Spikelets compressed, 3-many-flowered, the lower 1-4 lemmas empty ; glumes 

 compressed-keeled, acute or acuminate ; lemmas firm-coriaceous, compressed- 

 keeled, faintly many-nerved ; palea rigid, the keels broadly winged, 

 nearly marginal ; stamens 1 or 3. Erect perennials, with simple 

 culms, flat or involute leaves and terminal panicles. (Ancient name 

 of some plant, a diminutive of unio, unity.) 



* Panicle contracted, wand-like; spikelets few-flowered 



1. U. laxa (L.) BSP. Culms slender, 6-12 dm. high, in clumps 

 with knotted rootstocks ; leaves long and narrow; panicles 1.5-4.5 

 dm. long, the slender branches erect ; spikelets short-pediceled, 

 3-6-flowered, 5-7 mm. long; lemmas 3-4 mm. long, acuminate, 

 spreading at maturity; palea arched. (U. gracilis Michx.) 

 Sandy soil, L. I. to Fla., w. to Ky. and Tex. Aug., Sept. FIG. 158. 



* * Panicle expanded, nodding ; the spikelets many-flowered. 



2. U. latifblia Michx. Culms 6-15 dm. high ; sheaths shorter than the inter- 

 nodes, ligule 1 mm. long, lacerate; blades spreading, 10-22 cm. long, 0.5-2 cm. 

 wide, often ciliate at the base, margins scabrous ; panicle 



1-2.5 dm. long, the filiform branches bearing a few pendulous 

 broadly oval spikelets; these 1.5-3 cm. long, 6-12-flowered; 

 lemmas 9-12 mm. long, hispidulous on the winged keel; 

 stamen 1. Shaded slopes and low thickets, Pa. to Kan., and 

 southw. Aug., Sept. FIG. 159. 



3. U. paniculata L. (SEA OATS.) Culms stout, 9-15 dm. 

 high, with numerous long rigid leaves involute in drying; 

 ligule a ring of hairs about 1 mm. long ; panicles 2-3 dm. 

 long, the slender branches bearing many short-pediceled oblong- 

 oval stramineous spikelets; these 1-2 cm. long, S-W-flowered; 

 lemmas 8-10 mm. long, scabrous on the keel ; stamens 3. 

 Sand hills and drifting sands coast, Va. to Tex. Sept., Oct. 

 (Mex., S. A.) 



68. DISTfCHLIS Raf. SPIKE GRASS. ALKALI GRASS 



Spikelets dioecious, 8-16-flowered, compressed ; glumes 

 unegual, firm, keeled, acute ; lemmas coriaceous, rigid. 

 faintly many-nerved. Rigid erect perennials with exten- 

 sively creeping rootstocks, involute leaves and small crowded 

 K>o. D. spicata x i. panicles of large smooth spikelets. (Name from Slanxos, 



1 9 Spikelet and floret. two-ranked.) 



rf Floret. 1. D. spicata (L.) Greene. Pale or glaucous; culms 



168. U. laxa. 

 Spikelet x 3. 



159. u. 

 Spikelet xi. 

 Floret and lemma 

 x2. 



