56 Karl M. Wiegand and Arthur J. Eames 



b. Spikelets borne in a 2-rowed spike. 



c. Spikelets on opposite sides of the rhachis; spike solitary, terminal. 



2. Tribe Hokdeae 



c. Spikelets on one side of the rhachis, the spikes therefore one-sided ; spikes 

 solitary or several. 5. Tribe Chlorideae 



b. Spikelets in panicles, either open or spike-like, rarely in racemes. 

 c. Spikelets 2-many-flowered. 



d. Tip of the lowest flowering glume usually extending beyond the tips of the 

 small empty glumes, awnless or awned at the tip, more rarely just below 

 the tip or between the teeth. 1. Tribe Festuceae 



d. Tip of the lowest flowering glume usually reaching the tips of the large, 

 often broad, empty glumes, or shorter, usually with a bent awn inserted 

 on the back or between the teeth, more rarely awnless. 



3. Tribe Aveneae 

 c. Spikelets with one fertile flower. 



d. Spikelets bisexual, all alike. 



e. Sterile flowering glumes none (i. e., the flower solitary and fertile) ; 

 palet 2-nerved. 

 /. Palet usually smaller than the flowering glume and inclosed in it, 

 usually 2-keeled; articulation of rhachilla either above or below the 

 empty glumes. 4. Tribe Agrostideae 



/. Palet about equaling the flowering glume, 1-keeled ; articulation of 

 rhachilla below the empty glumes; (empty glumes minute). 



7. Tribe Oryzeae 

 e. Sterile flowering glumes 2 (i. e., spikelets 3-flowered but the two lower 

 flowers sterile) ; palet 1(2) -nerved. 6. Tribe Phalarideae 



d. Spikelets unisexual ; pistillate at summit of panicle, erect, linear-subulate, 

 awned ; staminate at base of panicle, drooping, elliptical, unawned ; rhachilla 

 articulated below the glumes. 8. Tribe Zizanieae 



a. Spikelets 2-flowered, the upper floret perfect, the lower one staminate or neutral 

 and often of a different texture; internodes between the florets usually unde- 

 veloped ; rhachilla articulated below the empty glumes. 

 b. First empty glume smaller than the second; the upper fertile flowering glume 

 cartilaginous or chartaceous, firmer than the empty glumes ; spikelets all 

 alike and not in special clusters as in the next tribe, without long silky hairs. 



9. Tribe Paxiceae 



b. First empty glume larger than the second ; the flowering glumes hyaline and much 



more delicate than the empty glumes ; spikelets in tiny clusters of 2 or 3, 1 fertile 



and 1 or 2 sterile or all fertile, with long silky hairs at base of flowering 



glume or on rhachis or pedicels. 10. Tribe Andropogoneae 



Tribe 1. Festuceae 

 a. Spikelets bisexual ; panicle generally open. 



b. Rhachilla naked or short-pilose ; plant not reed-like. 



c. Flowering glumes 5-many-nerved, sometimes cobwebby at base. 

 d. Spikelets not in dense 1 -sided bunches on the rays of the panicle. 

 e. Flowering glumes rounded on the back, with no cobwebby hairs. 

 /. Nerves of the flowering glumes not prominent. 



g. These nerves converging at apex of the acute flowering glume. 



/;. Spikelets more than 12 mm. long, rarely shorter ; flowering glumes 

 bifid at the apex, or more than 5-nerved, usually awned just below 

 the apex between or behind the teeth. 

 i. Grain pubescent at summit, adhering to the palet; stigmas inserted 

 below a hairy cushion-like appendage at summit of ovary. 



1. Bromus 

 i. Grain not pubescent, free ; stigmas terminal. 2. Bromelica 



