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. Rydberg’s n. 1822 (as in 
U.S. Herb.) well represents it and Mr. Clements’ n. 2925, from 
an intermediate station, still in Nebraska, may be referred here, 
though less canescently pubescent, and with leaves not at all 
subcordate. 
P. PROPINQUA. 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 ocre 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, Rydberg’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. RIGIDULA (Sheld.), Greene, Leafl. i, 24. Aquatic but 
rigidly erect, without floating leaves, 3 to6 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 2 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 fistulous 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, 
