104 Chaje — Notes on Genera of Panicex. IV. 



In the following synopsis and diagnoses this ideal spikelet is always in 

 mind, the same name being used for corresponding parts, even when the 

 first glume is wanting as in most species of Paspalum or when both 

 glumes are wanting as in Reimarochloa and in a few species of Paspalum, 

 the scale which appears to be a glume in the latter case, being the sterile 

 lemma. 



The type species of each of the genera here recognized, except Thrasya, 

 Odontelytrum and Dissochondrus, and of most of the generic names referred 

 to synonymy, is represented in the National Herbarium by specimens or 

 in a few cases by spikelets contributed from type specimens. 



Synoptical Key. 



Spikelets all alike (the lower of each pair aborted in Echinolaena). 

 Spikelets neither sunken in the cavities of a spongy rachis, nor 

 surrounded by an indurated leaf-sheath nor involucre-form 

 bracts. 

 Spikelets not subtended nor surrounded by bristles (sterile 

 branchlets ) , ( axis of branchlet extending beyond the base of 

 the uppermost spikelet as a point or bristle in Panicum, 

 subgenus Paurochaetium) . 

 Fruit cartilaginous-indurated, not rigid, papillose, usually 

 dark colored, the lemma with more or less prominent, 

 white hyaline margins not inrolled. ( Fruit not rigid in 

 Hymenachne, Reimarochloa and in a few species of other 

 genera, but texture and margin not as above.) 

 Spikelets awnless. 



Fruit open at hyaline summit 1. Leptocoryphium. 



Fruit not open at summit. 



Lemma boat-shaped, hyaline margins narrow 



2. Anthaeuantia. 

 Lemma convex with broad hyaline margin. 



Fruit lanceolate-acuminate ; second glume and sterile 



lemma unusually long-silky 3. Valota. 



Fruit elliptic, pubescence short or none. 



Inflorescence of slender racemes, digitately or sub- 



digitately arranged 4. Syntherisma. 



Inflorescence a capillary panicle .... 5. Leptoloma. 

 Spikelets with slender awns. 



Second glume reduced to a minute scale; sterile lemma 



with a straight awn 6. Chloridion. 



Second glume and sterile lemma with flexuous or tangled 



awns 7. Acritochaete. 



Fruit indurated, rigid (or if thin, not hyaline-margined). 

 Alternate spikelets facing in opposite ways, that is the first 

 glume alternately extrorse and introrse; inflorescence 

 a solitary, unilateral raceme, the margins of the con- 

 cave rachis partially embracing the subsessile spike- 

 lets 8. Thrasya. 



