60 MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 
[Puate 17.] 
17. Polygonum Mexicanum Small. 
Polygonum Pennsylvanicum Torrey, Bot. Mex. Bound. Surv. 178 (1859), not Lin- 
naeus; 8. Watson, Proc. Am. Acad. 18: 147. 
Oy-4 
Polygonum Mexicanwm Small, Bull. Torr. Club, 19: 556 (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 
em. long, .1-1 em. 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, 5 mm. long, very oblique, fringed with short bristles; pedicels 2.5-3 
mim. 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, somewhat 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. 
