< 
477 
Possess all or some of the characters assigned by Mr. Sheldon to 
the proposed Species, and’ the others show them in a greater or 
less degree. 
‘After some years of observation on this and other species of 
Polygonum, 1 would not place much value in size, for some of our 
common species under certain conditions grow but two or three 
inches tall, while again we find them elongating to six feet. As 
to the aquatic habitats, at all the localities where I have met with 
Pe emersum, I have found it ranging from almost dry ground to 
One or two feet of water, both in swamps, quiet margins of lakes 
and rivers and in fairly swift running currents. The amount and 
manner of branching, as well as the tumidity of the internodes, 
depends on the size and strength of the plants. The shape of the 
leaves and the amount of pubescence are of little or no value, for 
the same patches produce variously shaped leaves as well as a great 
Variation in the length of the petioles, and some plants may be 
glabrous while others are entirely covered with strigose pubes- 
cence. 
The specimens distributed from the collections of the Univer- 
Sity of Minnesota as P. emersum differ more from the usual state 
of that species than do the ones sent out as P. vigidulum, and I 
have seen but one other specimen that corresponds with them. 
This was collected in Scott’s Bluff county, Nebraska, by Rydberg, 
No. 349. | 
PoLyconum puNcCTATUM ROBUSTIOR n var. 
Robust, of a rather dull green color, nearly glabrous. Stem 
erect, 4-7 dm. long, often with a long, creeping or horizontal 
ase, more or less papillose, sometimes strigillose, leaves oblong 
or lanceolate, 3-17 cm. long, .5—4 cm. broad, paler on the lower 
Surface than on the upper and strongly punctate, often crisped 
and undulate; ocrez I-1.5 cm. long, strigillose, fringed with long 
bristles, loose, mostly inflated about the nodes, sometimes opened 
obliquely at branching nodes; ocreolz contiguous or imbricated 
entire, nearly naked; pedicels 3-4 mm. long; achene triquetrous, 
3 mm. long, broadly-oblong, minutely granular but rather shining. 
This variety is of aquatic habit, being characteristic of the bor- 
f ders of lakes, ponds and rivers. The creeping or horizontal bases 
often reach a length of three feet. The plants range from two to 
_ three times larger than the typical form and are showy on account mo 
