191S] The Grasses of Illinois 341 



Aristida tuberculosa Niitt. 

 Sca-beaeli Aristida (Fig. 127) 



Aristida tuberculata, Lapham '57, 545, 571. A. tuberculosa, Patterson '76, 

 50; Flagg '78, 281; Higley and Eaddin '91, 141; Huett '97, 129; McDonald '00, 

 103; Gleason '07, 182; Gleason '10, 148. 



Culms 6 to 20 inches tall, branched at the base, somewhat swollen 

 at the nodes ; sheaths loose, smooth ; blades 5 to 10 inches long, about 

 2 mm. wide, rough above ; panicle open ; glumes 2.5 cm. long, with 

 pointed tips ; awns jointed to the lemma and twisted at base into a 

 slender column nearly as long as the lemma. 



This species is most commonly found along the southern part of 



the Atlantic coast. It is also found along the Great Lakes and in the 



interior wherever there are sandy areas. 



ILLINOIS SPECIMENS: Without locality. Mead. COOK Co. Chicago, Babcock, 

 July, 1870. JO DAVIESS co. Without locality, Pepoon. Henderson co. Oquawka, 

 Patterson, Sept., 1872. lee co. Dixon, Seymour, Sept., 1882. mason co. With- 

 out locality, M. S. Bebb in 1861; -without locality. Hall in 1861 and Sept., 1876. 

 union CO. Cobden, Waite, Sept., 1884. 



21. MUHLENBERGIA Sclireb. 



This genus has one-flowered spikelets which in Illinois species are, 

 with one exception, borne in very narrow panicles. The glumes are 

 thin and usually sharp-pointed or awned. The lemma is also pointed 

 or awned and incloses the grain, thus differing from the nearly related 

 genus Sporobolus, in which the grain is free. The awns are variable 

 even in the same individual and do not afford good characters for the 

 separation of species. There is a short, usually hairy callus at the 

 base of the lemma. Many of the species have long, scaly rootstocks. 

 All Illinois species are perennial. The leaves are mostly long and nar- 

 row and the ligule is short and membranous. 



The species of Muhlenbergia are of little economic importance. It 

 is said that the species which inhabit damp ground are useful for hay 

 if cut before the stems become hard, but most of the species grow in 

 waste places and are usually looked upon as weeds. The long root- 

 stocks make them somewhat difficult to destroy ; thoro cultivation 

 is the only method of eradication recommended. M. mexicana, foliosa, 

 and racemosn are the only species likely to cause trouble in this state. 



a. Glumes minute, always less than one-fourth the length of the spikelet, the 

 first glume often wanting. M. schreberi 



aa. Glumes always more than one-fourth the length of the spikelet. 



b. Plants never from long, scaly rootstocks; leaves elongate and very nar- 

 row, usually involute. 

 c. Panicle open, with long, spreading branches; spikelets on long, capil- 

 lary pedicels ; glumes about one-half the length of the lemma. 

 ^ ' M. capillaris 



cc. Panicle narrow and spike-like; spikelets nearly sessile; glumes nearly 

 as long as the lemma, at least two-thirds its length. M. cuspidata 

 bb. Plants always from long, scaly rootstocks; leaves not elongate, seldom 

 becoming involute. 



