HITCHCOCK AND CHASE — NORTH AMERICAN GRASSES. 



57 



5. Cenchrus viridis Spreng. 



Cenchrus viridis Spreng. Syst. Veg. 1: 301. 1S25. " Guadalupa." In the 

 Krug and Urban Herbarium in tbe Berlin Botanical Museum is a specimen " ex 

 herb. Sprengel," ticketed " Cenchrus viridis Spreng. Guadeloupe. Bertero legit." 

 A second label bears the date " 1817-19." This specimen, which is doubtless the 

 type, consists of two flowering culms without the bases. 

 ^■^m^hTtrs-~m'cfy[ol^fis -Steud;-Syn. PI. Glum. 1 : 109. 1S54. " G. echinatus 

 { Hochst. Hrbr. nr. 12. a. Surinam." Two burs from this specimen were kindlj 

 sent by the director of the herbarium of the Paris Museum. 



Cenchrus echinatus var. viridis Spreng. ; Griseb. Fl. Brit. W. Ind. 556. 1864. 

 Presumably based on C. viridis Spreng. 



fCenchrus viridis var. macrocephalus Doell in Mart. Fl. Bras. 2 2 : 310. 1877. 

 " Humboldt extra Brasiliam legit." The type has not been examined. It would 

 appear to be a specimen with bristles longer than usual, such a specimen as 

 Hitchcock's no. 9910 from Cartagena, Colombia. 



fCenchrus rigidus Willd. ; Doell in Mart. Fl. Bras. 2 2 : 310. 1877. A herba- 

 rium name given as synonym of C. viridis var. macrocephalus. 



DESCRIPTION. 



Plants annual ; culms often rather robust, 30 to 100 cm. tall or more, usually 

 terete, erect from a more or less geniculate base, the lower internodes commonly 

 short, sparingly branching from the base or lower nodes, glabrous, or scabrous 

 below the spike only ; sheaths mostly overlapping, loose, keeled, glabrous ; ligule 

 ciliate, scarcely 1 mm. long; blades 

 thin, flat, lax, mostly 10 to 30 cm. long, \ 



6 to 12 mm. wide, rounded at the base, 

 scabrous on the upper surface, on the 

 margins, and on the midnerve beneath ; 

 spike usually short-exserted, 4 to 10 cm. 

 long, rarely longer, dense, the slender 

 axis minutely pubescent, the naked tip 

 2 to 4 mm. long ; burs depressed-globose, 

 the body about 4 mm. high, as broad or 

 broader, villous, tawny, the outer bris- 

 tles numerous, very slender, crowded 

 toward the base, the inner usually ex- 

 ceeding the body and the spikelets, erect or spreading, the lobes of the body 

 usually 6 to 8, interlocking at maturity ; spikelets usually 3, exceeding the body 

 of the involucre, mostly 4 to 4.5 mm. long, about 1.4 mm. wide; first glume 

 obsolete; second glume two-thirds to three-fourths as long as the subequal 

 sterile lemma and fruit. 





— C . ~C yL lsl>-*^r~H^t~ v^\J 



Fig. 



11. — Genchrus viridis. 

 type specimen. 



From the 



DISTRIBUTION. 



Open ground, often a weed in cultivated fields and waste places, Florida Keys, 

 Mexico, and the West Indies to Brazil; also in the Philippine Islands, Guam, 

 Siam, and northern Australia, doubtless introduced from America. 

 Florida : Key Largo, Chase 3931 ; Hitchcock in 1903. Upper Matecumbe Key, 



Pollard, Collins & Morris 145. Key West, Rugel 120. 

 Tamaulipas : Tampico, Palmer 155 in 1910. 

 Veracruz : Sanborn, Orcutt 3074. 

 115803—19 5 



