322 OHIO BIOLOGICAL SURVEY 



bristles ; outer empty glume less than one-half as long as the spikelet ; 

 fertile lemma only moderately convex, striate, finely and faintly trans- 

 verse-rugose or pitted. 



Several varieties are extensively cultivated for hay. If fed in 

 large quantities and too frequently, the hay is injurious to horses. 

 In cultivated fields and waste places. Also called German or Hun- 

 garian millet. July-Sept. Rather general. Escaped from cultivation. 



Pennisetum glaucum (L.) R. Br. Pearl-millet. A coarse annual grass, 

 with a solid stem, 3-8 ft. high, bearing cylindrical, spike-like panicles, 6-12 in. 

 long. Spikelets with 1 perfect flower and an additional vestigial lemma, sur- 

 rounded at the base by a cluster of bristles. Empty glumes small and hyaline. 

 Cultivated for fodder and for the grain which is used as food. Other related 

 species are cultivated as ornamental grasses. 



59. Cenchrus L. Sandbur-grass. 



Annual or perennial grasses with flat leaves and spikate inflor- 

 escence, the small clusters of spikelets covered by a prickly, bur-like 

 involucre which is deciduous with them at maturity. Prickles ret- 

 rosely barbed. Involucres with 2 or more spikelets. Spikelets 2- 

 flowered usually with one perfect flower and a second staminate or 

 vestigial flower; empty glumes shorter than the lemmas, unequal; 

 lemma and palet of the perfect flower chartaceous, the lemma not 

 inrolled at the margins ; grain free, inclosed in the glumes and the 

 prickly involucre. 



Cenchrus tribuloides L. Sandbur-grass. An annual ascending 

 or trailing grass with flattened, much-branched solid stems, y 2 -Z ft. 

 long, and a stout spike-like raceme of prickly burs, often partly en- 

 closed in the upper leaf sheath. Prickly involucres pubescent, the 

 prickles retrorsely barbed ; spikelets enclosed in the involucre ; fertile 

 lemma not inrolled at the margin ; somewhat indurated. 



A disagreeable, troublesome weed. In sandy soil and cultivated 

 fields. July-Sept. Lucas, Wood, Ottawa, Erie, Lorain, Cuyahoga, 

 Franklin, Highland, Gallia. 



