96 THE TRUE GRASSES. 



O O Palea coriaceous, two- 

 keeled, with a deep furrow 

 between the keels. 



105. Piptochsetium. 



2. Lodicules two (anterior) ; awns slender, 

 sometimes reduced to a mere point. 

 Palea simply membranaceous,. spike- 

 lets small. . . . 108. Muhlenbergia. 



(N.B. Compare Limnas.) 



IV. Flowering glume awnless. . 1O6. Milium. 

 ft. Rachilla with a pedicel-like prolongation be- 

 yond the palea. 



I. Both empty glumes much shorter than the 

 flowering glume, the latter with a straight, 

 terminal awn. . . . 100. Brachyelytrum. 

 II. Second empty glume one fourth shorter than 

 flowering glume, the latter with a terminal, 

 recurved awn. . . . 110. Podophorus. 



b. One $ and one $ (or sterile spikelet) in pairs on 

 each branchlet of a spike-like panicle, these branch- 

 lets deciduous at the time of fruiting. 111. Lycurus. 



c. spikelets surrounded at the base with numerous 

 sterile (and a few $ ) spikelets which are either re- 

 duced to bristles or delicate bracts. 



112. Perieilema. 



d. Spikelets dioecious, the ? solitary upon long pedi- 

 cels 107. Aciachne. 



B. Flowering glume usually hyaline or membranaceous at 

 maturity, at least more delicate than the empty glumes; 

 grain loosely or not at all enclosed. 



a. Stigmas sub-plumose (their very short hairs 

 springing from all sides), projecting from the apex 

 of the nearly closed glumes. 



a. Spikelets in a head which is surrounded by a 

 bell-shaped involucre formed by the uppermost 



leaves 113. Cornucopias. 



/3. Spikelets in a flattened (broader than long) head 



which is enclosed between two opposite inflated 



sheaths with thorn-like blades. . 114. Crypsis. 



y. Spikelets in a close, often shortened false spike, 



the upper leaf not forming an involucre. 



