90 



POACEAE 



3/ P. angustifolia (Muhl.) Britton. Slow streams: N. Y. and 

 Pa. to Fla. 



N. Y. Throughout, increasing southward. 

 N. J. Morris Co., apparently increasing southward. 

 Pa. Bucks Co. 



HYDROCHARITACEAE 

 1. Limnobium Rich. 

 1. L. Spongia (Bosc.) Rich. Shallow water: N. J. and Ont. to 

 Fla., Tex., Mo. and 111. 



Reported by Knieskern from Swimming River, Monmouth Co., 

 N. J. Not recently collected and otherwise unknown in the range. 



POACEAE* 



A. Spikelets articulated below the empty scales or a sub- 



tending involucre, or attached to and deciduous 

 with the internodes of a readily disarticulating 

 rachis, i-flowered, or if 2-flowered the lower im- 

 perfect, usually staminate; rachilla not extending 

 beyond the uppermost scale. 

 Spikelets round or dorsally compressed; hilum 

 punctiform. 

 Fruiting scale and palet hyaline, thin, much 

 more delicate in structure than the thick 

 membranous to coriaceous empty scales. 

 Spikelets unisexual, the pistillate borne in 

 the lower, the staminate in the upper, 

 part of the same spike. 

 Spikelets in pairs, one sessile, perfect, the 

 other pedicellate, perfect, staminate or 

 empty, sometimes reduced to a single 

 scale or wanting. 

 Fruiting scale and palet never hyaline and 

 thin, as firm as the empty scales, or 

 firmer. 

 Fruiting scale and palet membranous; 



spikelets naked, spiny (in ours). 

 Fruiting scale and palet chartaceous or 

 coriaceous, differing in color and appear- 

 ance from the remaining scales ; spikelets 

 sometimes enclosed in an involucre. 

 Spikelets laterally compressed; hilum linear. 



B. Spikelets articulated above the empty scales (below them 



in nos. 32, 34, 41, and 50) which are persistent, 

 i-many-flowered; rachilla sometimes extending 

 beyond the uppermost scale. 

 * Taxonomic treatment contributed by Mr. G. V. Nash. 



I. Maydeae. 



II. Andropogoneae. 



III. Zoysieae. 



IV. Paniceae. 

 V. Oryzeae. 



