GRASSES OF IOWA. 



273 



DESCRIPTION. 



Floating Manna ( rR vss. An erect grass, 3 to 5 feet (6-10 dm.) 

 high, with somewhat flattened culms, long leaves, and a narrow panicle, 

 1 foot (2.1 dm.) long. Lower panicle-branches finally spreading. Spike- 

 lets linear, cylindrical, \ to I inch (1-2 cm.) long, seven to thirteen- 



Fio. 189. Glycerin Americana a, -spikelet; Fig. 190. Glyceria fluitans-*, inflorescence, 



b, empty and flowering glumes. (Div. Agros. b, flowering glumes; c, spikelets. iDiv. Agros. L. 

 U. S. Dept. Agrl. I S. Dept. Agrl.) 



flowered; empty glumes broad, hyaline, faintly nerved near the base, 

 the first about U lines (3 mm.) long, the second a little longer; flower- 

 ing glumes about 3 lines (6 mm.) long, seven-nerved, scabrous, obtuse, 

 entire at the apex or obscurely toothed. Wet places, often in running 

 water. June to September. 



