138 MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 
[Puare 56.] 
56. Polygonum Watsoni Small. 
Polygonum imbricatum Nuttall; S. Watson, Am. Nat. 7: 665 (1873), not Raf., Bot. 
Calif. 2: 12; Porter, Bot. Wheeler Exp. 232; Porter & Coulter, Syn. Fl. Colo. 123; 
Coulter, Man. Bot. Rocky Mt. Reg. 319; Greene, Fl. Francis. 515. 
Annual, low, slender, glabrous and smooth except a slight scurfy roughening about 
the nodes. Stem erect, .5-1.5 dm. long, simple or sparingly branched, four-angled; 
leaves linear, 1-5 em. long, acute, divergent, those near the ends of the branches reduced 
to linear-lanceolate bracts, .4-1 cm. long, acute, crowded and imbricated, conspicuously 
articulated to the ocreae; ocreae funnelform, 2-4 mm. long, silvery, two-parted but early 
lacerate ; inflorescence axillary, consisting of clusters bearing several flowers, confined to 
the ends of the branches, appearing as terminal racemes; pedicels about 1 mm. long; 
calyx green, 2 mm. long, five-parted to below the middle, the segments ovate, obtusish, 
often somewhat colored on the margins, the outer ones not longer than the inner; 
stamens five or fewer, included; style .2-.3 mm. long, three-parted to below the middle, 
included; achene triquetrous, 1.5 mm. long, narrowly-oyoid, nearly black, prominently 
granular in ridges. 
Washington to Montana south to California and Colorado. 
