102 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
POACEAE. Grass FAmiIny. 
KEY TO THE TRIBES, 
Spikelets, 1 or 2-flowered. 
Rachilla articulated below the glumes, the spikelet 1 or 2-flowered, 
when 2-flowered the lower staminate. 
Glumes 2; spikelets flattened..............222-2-2-2-22------ ORYZEAE. 
Glumes apparently 3 or 4; spikelets not flattened............... PANICEAR. 
Rachilla articulated above the glumes. 
Glumes apparently 4; palea l-nerved ..............--.------- PHALARIDEAE. 
Glumes 2; palea 2-nerved...........2222.-2-2---2---2---0ee- AGROSTIDEAE. 
Spikelets 2 to many-flowered. 
Inflorescence a panicle or raceme. 
Lemma shorter than the glumes, usually with a bent awn arising 
from the back............-.-2...-.-.-.------------------- AVENEAE. 
Lemma longer than the glumes, awnless or with a straight apical 
AWN......222 222-2 ee eee FEsTUCEAE. 
Inflorescence a spike. 
Spikelets crowded in 2 rows, forming one-sided spikes........... CHLORIDEAE. 
Spikelets in 2 opposite rows._.-.-..------ 22-00-22 ee eee Horpeae. 
KEY TO THE GENERA, 
ORYZEAE, 
Flowers perfect; glumes and lemmas keeled........ 22.2... Homa.ocencurus (p. 104). 
PANICEAE, 
Spikelets in one-sided racemes or spikes. 
First glume very small .............-..-.--.----------. SYNTHERISMA (p. 104). 
First glume well developed ...........-....---------- Paspatum (p. 104). 
Spikelets not in one-sided racemes or spikes. 
Inflorescence dense; pedicels bearing bristles .......... JHAETOCHLOA (p. 106). 
Inflorescence loose; pedicels not bristly -.............. Panicum (p. 105). 
PHALARIDEAE., 
Spikelet with 3 florets, the uppermost perfect, the others stami- 
nate... 0... .2-- 2-2-2 2 ee ee ee eee eee eee ee eee SAVAsTANA (p. 106). 
Spikelet with 1 perfect floret, the lateral ones reduced to ster- 
ile lemmas. , 
Sterile lemmas bifid, awned ............ 2.2... -.-.... ANTHOXANTHUM (p. 106). 
Sterile lemmas awnless, very small........-...-.-.-.-- Puataris (p. 106). 
AGROSTIDEAE, 
Lemma with a long terminal awn, and closely embracing the 
grain. 
Fruiting lemma thin and membranaceous..-..... 2... . MUHLENBERGIA (p. 110). 
Fruiting lemma firm and indurated. 
Awns 3-branched. ..........----.-.------------ ARISTIDA (p. 107). 
Awns simple. 
Twisted, persistent on the lemma...........- Stipa (p. 107). 
Straight, deciduous from the lemma... .....-- Oryzopsis (p. 109). 
