POLYGONACEOUS GENERA. 31 
leaves, as well as the hispid peduncle in this phase, separate thie 
plant most definitely from its neighbor of a much lower alti- 
tude, P. Plattensts. 
P. LATEVIRENS. Riparian. Prostrate rooting stems tortuous, 
short-jointed, the internodes little more than an inch long, more 
than half the nodes sending up a decumbent or upright densely 
leafy and terminally floriferous branch 6 to 10 inches high: 
leaves of a remarkably light and even yellowish green, elliptical 
to oblong-lanceolate, rarely more truly lanceolate and with 
broader and subcordate base, 24 to 33 inches long, on petioles of 
+ to? inch, glabrous on both faces but the margin varying from 
perfectly entire to scabrous-denticulate and even serrulate-cilio- 
late: spikes very short-peduncled, almost subsessile among the 
numerous leaves at summit of the branch, very short and thick, 
almost round-ovyoid; bracts broad-ovate, cuspidately acute, 
glabrous. 
This fine species well marked in habit, I know only in speci- 
mens distributed by Mr. Baker from near Gunnison, southern 
Colorado, 1891, his distribution number 806. The numerous 
very leafy stems, so crowded on the prostrate main stem, must 
appear in a singularly compact mass or bed. 
P. PSYCHROPHILA. Aquatic, though apparently in shallow 
water, internodes about 2 inches long; leaves thin, oblong-lan- 
ceolate, acute, rounded at base but not subcordate, 3 or 4 inches 
long, glabrous, on not very slender petioles of about 2 inches: 
uppermost ocree (perhaps emersed) developing a broad green- 
herbaceous lobed and wavy rim: spike short-ovoid, less than an 
inch high, on a glabrous peduncle of less than an inch; bracts 
broad, pointless. 
Seen only in the herbarium of Mr. Osterhout, who collects it 
in a subalpine lake in Estes Park in northern Colorado. The 
nature of the ocree would seem to indicate affinity for P. Hart- 
wrightii, yet itis hardly of that group. 
P. Oreaana. Riparian. Stoutish, short-jointed: lowest 
leaves (perhaps floating when young) oblong-lanceolate, subcor- 
date, 3 or 4 inches long, on stout petioles of less than an inch, 
bright-green, glabrous; those above them smaller, oblong or 
elliptical, more or less villous or hirsute especially along the 
