ACiKOSTlDE.E. 189 



Tribe VIII.— AGROSTIDEiE. 



Spikelets usually containing 1 perfect flower each, racliilla 

 sometimes prolonged beyontl the palea. Empty glumes 2 (none in 

 Coleanfhns, 4 in some species of SporohulKs and Muldenbergia), 

 usually as long as the floral glume or longer; palea (wanting in 

 Alopecurits and some species of Agrosiis) 2-uerved or nerveless 

 (1-nerved in Cinna). Grain not furrowed, embryo small. 



This large tribe is one of the most difficult to circumscribe satis- 

 factorily, or to divide into definite genera. Their general character 

 is to have a single flower in each spikelet. either terminal or with a 

 slight bristle-like continuation of the racliilla. The single flower in 

 the spikelet wliich separates the tribe from the following ones is 

 not so positive a character, as it occurs also in one genus of Avenese, 

 in a few genera of Chloridefe, and occasionally in Festuce^. 



Trinius divided this tribe into three subtribes: Vilfese, with the 

 callus scarcely prominent or obsolete; Agrostefe, with the callus 

 globular; and Stiiieae, witli the callus obconical. But the callus is 

 not an appendage to tlie base of tlie floral glume, as he would have 

 termed it, but only the upper part of the racliilla, to which the glume 

 and the enclosed floret are attached. Its shape depends on the dis- 

 tance at which the floral glume is attached above the empty ones, a 

 distance very variable throughout the Order. The length of the 

 joint of the racliilla is a useful character, but never ranks as sub- 

 tribal. 



A. Floral glume firmer than the empty glumes and very closely en- 

 veloping the grain. 



a. Spikelets each containing 1 perfect flower (b) 



b. Floral glume entire, bearing a terminal 3-branched 

 awn, the lateral branches often very short oi- some- 

 times obsolete 45 



b. Floral glume 2-toothed, awn usually simple. 



twisted and bent (c) 



c. Lodicules usually 3, floral glume and jialca be- 

 coming very hard (d) 



