POLYGONACBOUS SENEEA. 31 



leaves, as well as the hispid peduncle in this phase, separate the . 

 plant most definitely from its neighbor of a much lower alti- 

 tude, p. Plattensis. ' 



P. LiETBViKEKS. Eipariau. 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, %h to 3 J inches long, on petioles of 

 J to f 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-ovoid ; 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. PSYCHKOPHiLA. Aquatic, though apparently in shallow 

 water, internodes about 3 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 3 inches : 

 uppermost ocreae (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 herbai'ium of Mr. Osterhout, who collects it 

 in a subalpine lake in Estes Park in northern Colorado. The 

 nature of the ocrese would seem to indicate affinity for P. Hart- 

 wrightii, yet it is hardly of that group. 



P. Orbgana. Eiparian. 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 



