18 



tt Setie antrorsely scabrous. 



i Flowering glume smooth or nearly so. 



§ Rachvi scabrous. 



8. CHiETOCHLOA AMBIGTJA (Guss.) n. comb. Setar ia verticillata \ar. amhigua 



Guss. Prodr. 1: 80 (1827). Setaria ambigua Guss. Fl. Sic. Syn. 1: 114 (1842). 



Not ;S'etoria ambigua Schrad. Linnsea 12: 430 (1838). (Fig. 7.) 



A csespitose, erect, much branchied annual, 2 to 5 dm. high, with compressed culms, 



lanceolate leaves, and rather loose spicate ]ianicles 4 to 10 cm. long. Culms 



geniculate at the base, glab- 

 rous, leafy, the nodes brown, 

 glabrous; sheaths striate, 

 compressed, loose, about 

 equaling the internodes, thin, 

 glabrous, the margin ciliate 

 above; ligule about 1 mm. 

 long, densely ciliate-fringed* 

 with white hairs, which are 

 1 mm. long or less. Leaf- 

 blades lanceolate, cordate at 

 the base, long-acuminate at 

 the apex, 5 to 15 cm. long, 

 6 to 15 mm. wide, scabrous 

 on both sides and on the 

 cartilaguaous margins. Axis 

 of the inflorescence chan- 

 neled, scabrous, but not pi- 

 lose; branches short, sub- 

 verticillate, densely flowered, 

 the lower rather remote; 

 setse solitary, stout, some- 

 what flexuous, antrorsely 

 scabrous, 4 to 8 mm. long. 

 Spikelets elliptical, 2 to 2.5 

 mm. long; first glume tri- 

 angular-cordate, 3-nerved, 

 claspmg the base of the 

 spikelet and about one-third 

 its length; second and third 

 glumes equaling the flower- 

 ing glume in length, obtuse, 

 5 to 7 nerved, the third with 

 a palea; flowering glume 2 

 mm. long, elliptical, sounded 

 at the apex, striate, very finely transversely wrinkled, not rugose. Palea similar 

 in texture and markings. 

 Collected on "ballast," Camden, N. J., by F. Lamson-Scribner, 1884, and at Mobile, 



Ala., by Chas. Mohr, 1884. 

 An adventitious European annual with tlie habit and inflorescence of C. verticil- 

 lata (L.) Scribner, 1)ut readily distinguished from that species by its ha\dng 

 the setic antrorsely instead of retrorsely scabrous. Distinguished from C. 

 viriditi (L.) Scriljner, by its loose, subverticillate panicles and scabrous, not 

 pilose, rachis. 



Fig. 7. — Chcetochloa amhigua: a, spikelet showing seta; 6, c, 

 views of the spikelet; d, flowering glume, dorsal view. 



