POLTGOKAOBOTJS GBNBRA. 29 



rounded or truncate at base, the petioles 3 or 4 inches long, those 

 of the uppermost showing some trace of hairs in the form of a 

 diminutive muriculation : spikes commonly 2, strictly cylindricj 

 longer and narrower than in the aquatic state. 



This, as I apprehend it, is a northern midland homologue of 

 P. fiuitans, distinguishable in even its aquatic condition by the 

 vivid green and the large dimensions of its leaves, as well as a 

 different outline. The specimens are from the Upper Missis- 

 sippi valley, from Indiana to Iowa and Minnesota. I am not 

 without a fear that what I here describe is an aggregate, even as 

 to the aquatic specimens. I therefore indicate as typical a 

 sheet in the U. S. Herb, from Miller's, Indiana, 24 June, 1896, 

 by L. M. Umbach. Beautiful Minnesota specimens, such as 

 Ballard's, from Oshawa, Nicollet Co., Sandberg's, from Center 

 City, and of Burglehaus from near Minneapolis all fail to ex 

 hibit the subcordate leaf -base. Yet, the riparian specimen, in 

 which the subcordate character comes out strongly, is from 

 Minnesota, at Fond du Lac, by F. F. Wood. 



Similar plants from farther westward, like some from Ne- 

 braska, may or may not be of this species. 



P. PLATTBNSis. Riparian. Leafy and floriferous terminal of 

 stems assurgent, i foot high or more, the elongated and pros- 

 trate portions rooting in mud, and with internodes 4 to 7 inches 

 long, each node often emitting a short sterile leafy upright 

 branch, the leaves of such oval to lanceolate and 1 to 3 inches 

 long, glabrous or pubescent ; but foliage of main stem under 

 the spike much longer, often 4 inches long, \\ in. breadth, sub- 

 cordately ovate-lanceolate, acute, bright green and glabrous, or 

 more usually with a distinct pubescence along margin and mid- 

 vein, the stoutish petioles an inch long or more : ocreae all thin 

 and hyaline, glabrous : spikes cylindric, 2 inches long or some- 

 what less and narrow, their peduncles glandular-pubescent ; 

 bracts broad-ovate, scarcely acute, glabrous or with some short 

 hairs toward the base. 



Aquatic state (?). Floating leaves thin, oblong, obtuse at both 

 ends, 2 or 3 inches long, glabrous : peduncle and bracts of the 

 short oval spike also glabrous. 



Riparian type from the North Platte River at Fairbanks ia 



