go MEMOIES FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 



[Plate 17.] 

 17. Polygonum Mexicanum Small. 



Polygonum Pennsijlvanicum Torrey, Bot. Mex. Bound. Surv. 178 (1859), not Lin- 

 naeus; S. Watson, Proc. Am. Acad. 18: 147. 



Polygonum Mexkanmn Small, Bull. Torr. Club, 19: 356 (1892). 



Annual, slender, pale green, glabrous as far as the upper branches. Stem erect, 

 4-7 dm. tall, more or less branched, the upper parts slightly pubescent, becoming 

 glandular about the inflorescence; leaves varying from linear-lanceolate to linear, 3-12 

 cm. long, .1-1 cm. broad, broad, firm, obscurely punctate, ciliate, inclined to be revo- 

 lute, short-petioled ; ocreae cylindric when young, .5-1.5 cm. long, thin, clasping the stem 

 closely when young, at length becoming loose, sparsely hispidulous or nearly smooth, 

 eciliate ; inflorescence paniculate, pubescent or glandular, the ultimate divisions ending 

 in spicate geminate racemes; racemes oblong, 1.5-3.5 cm. long, erect, densely flowered; 

 ocreolae funnelform, 3 mm. long, very oblique, fringed with short bristles; pedicels 2.5-3 

 mm. long ; calyx light rose color, 2-3 mm. long, five-cleft to the middle or to near the 

 base; stamens six to eight, included; style 1-1.5 mm. long, two-parted to below the 

 middle, s(jmewhat exserted ; achene lenticular, 3-4 mm. long, ovoid or broadly ovoid, 

 flat, but inconspicuously gibbous on one side, thick-pointed, dark brown or nearly black, 

 mostly granular and dull. 



Southern Louisiana and southern Texas to Sonora, Jalisco, Michoacan and San 

 Luis Potosi. 



