GRAMINEAE (GRASS FAMILY) 95 



6. SORGHASTRUM Nash 



Spikelets sessile at each joint of the slender rhachis of the peduncled racemes, 

 which are reduced to 2 or 3 joints, the sterile spikelets reduced (in our species) 

 to hairy pedicels ; glumes indurated as in Andropogon ; sterile lemma thinly 

 hyaline, the fertile lemma reduced to hyaline appendages to the strong awn ; 

 palea obsolete. — Perennial grasses with tall stout culms, the racemes arranged in 

 open panicles. (Named from its resemblance to Sorghum.) 



1. S. nutans (L.) Nash. (Indian Grass, Wood Grass.) Culm simple, 

 1-2 m. high ; leaves 6-10 mm. wide, scabrous, glaucous ; sheaths 

 smooth ; panicle narrowly oblong, at first open, contracted after 

 flowering, 1-3 dm. long ; the spikelets lanceolate, at length 

 drooping, yellowish or reddish brown and shining, clothed, 

 especially toward the base, with fawn-colored hairs ; the 

 twisted awn longer than the spikelet. {Andropogon L. ; Chryso- 

 pogon Benth.) — Dry soil, Me. to Man., and southw. Fig. 53. 



Sorghum halepense (L.) Pers., Johnson Grass, a more 

 robust plant, is found as an escape or a weed, chiefly along 

 the southern border of our range. It differs from Sorghastrum 

 in having two pediceled spikelets (of the group of three) stami- 53 s_„mn„y >^.,. 

 rate or empty ; and in having a more spreading panicle and a 

 firmer lemma. This is thought by some to be the original of the cultivated 

 sorghums. (Introd. from Eu. ) 



6. DIGITArIA Scop. Finger Grass 



Spikelets 1-flowered, lanceolate-elliptic, sessile or short-pediceled, solitary 

 or in 2's or 3's, in two rows on one side of a continuous narrow or winged 

 rhachis, forming simple slender racemes which are aggregated toward the summit 

 of the culm ; glumes 1-3-nerved, the first sometimes obsolete ; sterile lemma 

 5-nerved ; fertile lemma leathery-indurated, papillose-striate, with a hyaline mar- 

 gin not inroUed, inclosing a palea of like texture. — Annual, mostly weedy 

 grasses, with branching culms, thin leaves, and subdigitate inflorescence. 

 (Name from digitus, a finger.) Syntherisma Walt. 



* Hhachis of racemes with angles loingless ; first glume obsolete ; culms erect. 



1. D. filif6rmis (L.) Koeler. Usually tufted, branching and leafy at the base ; 

 culms slender or almost filiform, 2-7 dm. high; lower sheaths hirsute; blades 

 0.5-2 dm. long, 4 mm. or less wide (rarely wider), hirsute or glabrous on the 

 lower, scabrous on the upper surface ; racemes 1-5, unequal, 3-10 cm. (rarely 

 15 cm.) long, very slender; spikelets 1.7 mm. long, mostly in 3's, appressed, 

 the second and third on slender flexuous pedicels ; glume and sterile lemma 

 densely or sparsely villous between the nerves with white gland-tipped hairs; 

 the glume shorter and narrow, exposing the dark brown acute fertile lemma. 

 {Panicum L.) — Sterile or sandy soil, N. H. to Mich., I. T., and southw. 

 July-Sept, 



2. D. villbsa (Walt.) Ell. Similar to the preceding, usually taller, less slen- 

 der and more densely and constantly hirsute on the sheaths arid on both surfaces 

 of the blades; racemes 2-8, more distant (sometimes 3 cm. apart), 5-20 cm. 

 long, much interrupted toward the base ; spikelet-clusters usually rather dis- 

 tant ; spikelets 2.25 mm. long; the glume and sterile lemma densely matted- 

 villous between the nerves with gland-tipped hairs. — Sandy soil, Va. to Mo., and 

 *^outhw. July-Oct. 



* * Bhachis of racemes with lateral angles winged; culms spreading. 



-t- Pedicels terete ; first glume obsolete. 



3. D. HUMirtjsA Pers. Glabrous ; culms 1.5-4 dm. high, much branched 

 below, ascending or nearly prostrate ; leaves 2-10 cm. long (rarely longer), 3-6 

 mm, wide: racemes 2-6, aggregated, divergent, often curved, 3-10 cm, long: 



