266 OHIO BIOLOGICAL SURVEY 



Paniceae. 



I. Spikelets without a subtending involucre. 



1. Spikelets arranged in true panicles. Panicum. (53) 



2. Spikelets arranged in 1-sided recemes, sometimes paniculate. 



(1). Fruiting flowering glumes chartaceous, with flat hyaline margins. 



a. Spikelets long-pediceled, in a diffuse pinacle. Leptoloma. (54) 



b. Spikelets on slender spike-like, often digitate branches of the in- 



florescence. Syntherisma. (55) 



(2). Fruiting flowering glumes indurated, rigid, the margins inrolled, not 

 hyaline. 



a. Some of the glumes awned; spikelets crowded in 1-sided branches 



of the panicle. Echinochloa. (56) 



b. Glumes awnless ; spikelets plano-convex, on secund branches of the 



inflorescence. Paspalum. (57) 



II. Spikelets with an involucre of bristles or a prickly bur. 



1. Spikelets subtended by bristles. Chaetochloa. (58) 



2. Spikelets enclosed in a globular, prickly, bur-like involucre. Cenchrus. (59) 



Oryzeae. 



1. Spikelets much flattened laterally, with bisporangiate flowers. 



Homalo cenchrus. (60) 



2. Spikelets monosporangiate. 



a. Spikelets intermixed in the panicle. Zizaniopsis. 



b. With carpellate spikelets in the upper part of the panicle and staminate 



spikelets below. Zizania. (61) 



Andropogoneae. 



1. Inflorescence paniculate, decompound. 



a. Pedicellate spikelet present; stem solid. Holcus. (62) 



b. Pedicellate spikelet wanting; stem hollow. Sorghastrum. (63) 



2. Inflorescence simple or compound made up of 1 or more spike-like racemose 



branches. 



a. Spikelets alike, all with bisporangiate flowers; rachis of the inflorescence 



branches continuous. Miscanthus. (64) 



b. Sessile spikelets bisporangiate, with awns, the pedicellate spikelets staminate 



or empty ; inflorescence simple or with 6 or less digitate branches. 



Andropogon. (65) 



Maydeae. 



1. Carpellate spikelets inclosed in pockets of the internodes of the enlarged and 



flattened rachis; rachis breaking into joints at maturity; inflorescence stam- 

 inate above, carpellate below. 



a. Carpellate inflorescence not covered with husks. Tripsacum. (66) 



b. Carpellate inflorescence covered with husks. Euchlaena. 



2. Carpellate spikelets covered by a bony leaf-sheath or collected in an ear covered 



with husks. 



a. With a bony leaf-sheath covering the single large grain. Coix. (67) 



b. With numerous grains in an ear covered with husks, or with husk-like 



glumes around the grains. Zea. (68) 



