POLYGONACEOUS GENERA. 39 



self more than forty years since, taken from the margin of a 

 shallow pond near Albion, Dane Co., Wisconsin. It ranges 

 westward into Nebraska, where Mr. Eydberg's n. 1833 (as in 

 U. S. Herb.) well represents it and Mr. Clements' n. 3935, from 

 an intermediate station, still in Nebraska, may be referred here, 

 though less canescently pubescent, and with leaTes not at all 

 subcordate. 



P. PKOPINQUA. Near the last, more nearly aquatic and 

 decumbent, only the growing foliage canescent, and that 

 almost silvery ; lower and mature leaves elliptic-lanceolate, not 

 subcordate, rather acutish at base, 4 or 5 inches long, obscurely 

 and minutely strigulose-roughened on both faces, but the mid- 

 vein beneath beset with a stout but sharply hair-pointed muricu- 

 lation rather than pubescence, neither the ocrese nor the stem 

 obviously pubescent : spikes thicker, and flowers larger than in 

 the last ; peduncles merely glandular-scabrous ; bracts from 

 scabro-hispid to rather obviously strigose. 



Species known only from South Dakota, Eydberg's n. 986 

 (in U. S. Herb.) from the Black Hills, being the type ; a more 

 pubescent form having been collected by T. A. Williams at 

 Brookings, in 1889. 



P. BiGiBTTLA (Sheld.), Greene, Leafl. i, 34. Aquatic but 

 rigidly erect, without floating leaves, 3 to 6 feet high ; immersed 

 internodes thick and fistulous, tapering upward from each node : 

 leaves about 5 to 7 inches long on ascending petioles of about 

 3 inches, triangular-lanceolate, slenderly tapering above, broad 

 and nearly truncate at base, glabrous on both faces, the reduced 

 floral or uppermost finely strigulose and puncticulate ; peduncles 

 about 3 inches long, glandular-hispidulous, spikes rather longer, 

 thick and large-flowered ; bracts ovate, sparingly somewhat 

 glandular-hispidulous : achenes orbicular, smooth, polished. 



Certainly very distinct, as Mr. Sheldon has demonstrated, the 

 leaf -outline being altogether peculiar, as also the flstulous and 

 somewhat conical internodes of the submersed parts of the stem. 

 The above diagnosis is based on a fine sheet of Ballard's collect- 

 ing at Nicollet, cited by Mr. Sheldon. But according to U. S. 

 Herb, the species ranges westward to the vicinity of Bozeman, 



