1918] The Grasses of Illinois 285 



Without locality, Pepoon 182. kankakee co. Kankakee, De Selm, Sept., 1913; 

 Altorf, Hill, July, 1873. macon go. Decatur, Clokey, Sept., 1898. mason CO. 

 Without locality, M. S. Bebb in 1861. peoria CO. Peoria, Brendel; Peoria, Mc- 

 Donald, Aug., 1889. ST. CLAIR CO. Mascoutah, Welsch. 



8. PASPALUML. 



This genus includes a large number of species, most of which arc 

 found in Avarm climates. None of the species are abundant in the state ; 

 for the most part they are found in the southern half. The inflo- 

 rescence consists of spike-like racemes which are racemose along the 

 main axis. The spikelets are flat on one side and strongly convex on 

 the other, many of them almost hen'iispherical. They are frequently 

 arranged in pairs on the rachis. These grasses are of no economic im- 

 portance in the state, as they grow mostly in wet or sandy soil and 

 are not common. The leaves are long and narrow, and often pubescent. 

 The amount of pubescence present is quite variable on all parts of the 

 plant. 



a. Eachis thin and leaf-like, more than 2 mm. broad. 



b. Spikelets pubescent, 1.5 mm, long, elliptical; blades 1 to 6 inches long, 



6 to 14 mm. broad. -P. repens 



bb. Spikelets smooth, 2 mm. long; leaf -blades 2 inches or less long, 2 to 6 



mm. broad. P- dissectum 



ail. Pachis never, thin and leaf-like, le^s than 1 mm. broad. 



b. Spikelets pubescent, arranged in pairs. 



c. Spikelets less than 2 mm. long, usually 1.5 mm., usually glandular 



spotted ; blades densely pilof-e. P. setaceum 



cc. Spikelets 2 mm. or more long, not glandular spotted; leaves velvety, 



the whole plant grayish. P. bushii 



bb. Spikelets smooth. 



c. Blades ciliate on the margin, the surfaces of the blade either smooth 

 or pubescent ; spikelets in pairs, 

 d. Surfaces of blades smooth or with a few very fine hairs, 

 e. Spikelets about 2 mm. long, always more than 1.7 mm. 



f. Spikelets green; culms erect; blades usually smooth; 

 spikelets averaging 2 mm. in length. P. ciliatifoliuni 

 ff. Spikelets yellowish or straw color; culms always spread- 

 ing; blades usually with a few fine hairs on the upper 

 surface; spikelets usually more than 2 mm. long. 



P. straminnnn 



ee. Spikelets 1.5 to 1.7 mm. long; leaves usually ciliate on the 



midnerve. P. longepedunciilatum 



dd. Surfaces of blades, both upper and under, densely pubescent: 



plants erect; spikelets 2 to 2.5 mm. long. P. muhlcnhergii 



ec. Blades not cilinte on the mnrgin ; spikelets usually arranged sinfily. 



d. Blades conspicuously pubescent. 



e. Spikelets about 2 mm. long, arranged in pairs; culms spread- 

 ing or prostrate. P. supimim 

 ee. Spikelets 2.5 to 2.8 mm. long, arranged singly; sheaths and 

 blades long pilose; culms erect. P. longipilum 

 dd. Blades smooth or slightly pubescent; spikelets arranged singly. 

 e. Spikelets 3 to 3.2 mm. long; leaf-blades and lower sheaths 

 with a few hairs; blades reaching the base of the panicle 

 or exceeding it. P. circular e 

 ee. Spikelets 2.5 to 2.9 mm. long; plants smooth; panicle much 

 exceedinsr the blades. P. lacve 



