MANUAL OF THE GRASSES OF THE UNITED STATES 725 



Figure 

 ravennae 



Figure 1616.— Distribution of 

 Erianthus giganteus. 



144. ARTHRAXON Beauv. 



Perfect spikelets awned, sessile, the secondary spikelet and its 

 pedicel wanting or present only at the lower joints of the filiform 

 articulate rachis ; racemes terminating the branches of a dichotomously 

 forking panicle, in appearance subdigitate or fascicled. Usually 

 low creeping grasses with broad cordate-clasping blades and subflabel- 



late panicles. Type species, Arthraxon ciliaris 



Beauv. Name from Greek arthron, joint, and 



axon, axis, alluding to the jointed rachis. 

 1. Arthraxon hispidus 



var. cryptatherus (Hack.) 



Honda. (Fig. 1618.) Annual ; 



culms slender, branching, 



decumbent or creeping, 30 to 



100 cm long; sheaths hispid; 



blades ovate or ovate-lanceo- 



^x'T^cuJtT late > 2 to 4 .° m lon £> 5 to 15 

 mm wide, ciliate toward base ; 



panicle mostly 3 to 4 cm long, flabellate, contracting toward maturity; 



rachis joints slender, glabrous; spikelets 3 to 4 mm long, nerved, 



aculeate-scabrous, the awn short or wanting, an occasional pedicellate 



spikelet developed at the base of the raceme, 



similar to the sessile spikelets. o — Pastures, 



lawns, and open ground in a few localities, | 



Pennsylvania to Florida; Missouri, Arkansas; ( | 



Portland, Oreg.; introduced from the Orient 



(fig. 1619). 



145. ANDROPOGON L. Beardgrass 



Spikelets in pairs at each node of an articulate 

 rachis, one sessile and perfect, the other pedicel- 

 late and either staminate, 

 neuter, or reduced to the 

 pedicel, the rachis and 

 the pedicels of the sterile 

 spikelets often villous, 

 sometimes conspicuously 

 so; glumes of the fertile 

 spikelet coriaceous, nar- 

 row, awnless, the first 

 rounded, flat, or concave 

 on the back, several-nerved, the median nerve weak or wanting; sterile 

 lemma shorter than the glumes, empty, hyaline; fertile lemma hyaline, 

 narrow, entire or bifid, usually bearing a bent and twisted awn from 

 the apex or from between the lobes; palea hyaline, small or wanting; 

 pedicellate spikelet awnless, sometimes staminate and about as large 

 as the sessile spikelet, sometimes consisting of one or more reduced 

 glumes, sometimes wanting, only the pedicel present. Rather coarse 

 grasses (perennial in the United States), with solid culms, the spikelets 

 arranged in racemes, these numerous, aggregate on an exserted 



Figure 1619. — Distribution of 

 Arthraxon hispidus var. 

 cryptatherus. 



Figure 1618.— Arthraxon his- 

 pidus var. cryptatherus, X 1. 

 (Cult.) 



