G KAMI WEAK. 67 



Flowering scales with their sides turned to the rachis. 



Spikelets i-2-flowered in slender articulate spikes. 97. Lepturus. 



Spikelets 2-many-flowered in stout inarticulate spikes (articulated in one 



species). 98. Agropyron. 



Spikelets 2-6 at each joint of the rachis; scales mostly long-awned. 

 Spikelets i-flowered or with the rudiment of a second flower. 



99. Hordeum. 

 Spikelets 2-many-flowered. 



Rachis of the spike articulated, readily breaking up into joints. 



100. Sitanion. 

 Rachis of the spike continuous, not breaking up into joints. 



Empty scales a little smaller than the flowering ones. 



101. Elymus. 

 Empty scales very small or none. 102. Hystrix. 



Tribe XII. BAMBUSEAE. 



Tall canes with large flat spikelets in panicles or racemes. 103. Arundtnarta, 



x. TRIPSACUM L. 



Tall perennial grasses with thick rootstocks, rather broad, flat leaves and monce- 

 cious flowers. Spikelets i-2-flowered, in terminal or axillary, solitary or clustered, 

 elongated spikes. Staminate spikelets in 2's at each node of the upper part of the axis. 

 2-flowereri Insisting of four scales, the two outer coriaceous, the two inner thinner, 

 the palet hyaline; stamens 3. Pistillate spikelets in excavations at the lower joints 

 of the spike, I -flowered; stigmas exserted; style slender. Grain partly enclosed in 

 the excavations of the spikes, covered in front by the horny exterior lower scale. 

 [Name from the Greek, in allusion to the polished outer scales.] About 3 species, 

 natives of tropical and temperate America. Besides the following, another occurs 

 in the southern United States. 



I. Tripsacum dactyloides L. GAMA-GRASS. (I. F. f. 210.) Rootstock 

 1.25-2.5 cm. thick, culms stout, erect, 1-2 m. tall. Leaves smooth and glabrous, 

 3 dm. or more long, 1.25-3.75 cm. wide; spikes terminal, and in the upper axils, 

 solitary or 2-3 together, 1-1.25 dm. long; outer scales of the staminate spikelets 

 linear and obtuse, 8 mm. long, about 2 mm. wide, faintly many-nerved; exterior 

 scale of the pistillate spikelets horny, shining. In swamps or along streams, Conn, 

 to Kansas, south to Fla. and Tex. June-Sept. 



2. ERIANTHUS Michx. (See Appendix.) 



Tall, generally robust, perennial grasses, with thick creeping rootstocks, long 

 flat leaves, and perfect flowers in terminal panicles. Spikelets generally with a 

 ring of hairs at the base, 2 at each node of the jointed rachis, one sessile, the other 

 with a pedicel, generally I -flowered. Scales 4, the two outer indurated, the inner 

 hyaline, the fourth bearing a terminal straight or contorted awn; palet small, hya- 

 line; stamens 3. Grain oblong, free, enclosed in the scales. [Greek, referring to 

 the woolly spikelets.] About 17 species, natives of the temperate and tropical re- 

 gions of both hemispheres. Besides the following, four others occur in the Southern 

 States. 



Awn spiral. i. E. alopecuroides. 



Awn straight. 



Panicle lax; branches long and spreading; basil hairs longer than the outer scale 



of the spikelet. 2. E. saccharoides. 



Panicle compact or strict; branches short and erect or appressed; basal hairs equal- 

 ling or shorter than the outer scale of the spikelet. 



Outer scale about 5 mm. long. 3. E. compactus. 



Outer scale about 8 mm. long. 4. E. brevibarbis* 



I. Erianthus alopecuroides (L.) Ell. SPTRAL-AWNED PLUME-GRASS. 

 (I. F. f. 211.) Culms stout, erect, 1.5-3 m. tall, the summit and the axis of the 

 panicle densely pubescent. Sheaths glabrous; leaves 1.5-6 dm. long, 1.25-2.5 cm. 

 wide; panicle oblong, 1. 5-3 dm. long, 5-7.5 cm. wide, branches spreading, 7.5-12.5 



