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1078. P. paueiflorus, Ph., var. niagarensis, Gray. 
P. niagarensis, Tuck. 
With the same general characteristics as the species, but more 
robust, and more apt to be in running water, though not 
exclusively so. Leaves longer, (1£ to 3^- inches in length) and 
plainly 8 to 5 nerved, spikes 6 to 12 flowered. Same range. (B. P.) 
1074. P. pusillus, L. 
Frequent in still water, 2 to 3 feet deep, at South Chicago, and in 
pools and ditches at Englewood. July — August. (B.) 
In both localities will be found forms with the leaves almost setace- 
ous, (var. tenuissimus, Koch.) 
1075. P. mucronatus, Schrad. 
Common in ditches, near B. & 0. R. R. shops, South Chicago. 
June — July, 1880-’81. (B. P.) 
1076. P. pectinatus, L. 
Common in streams and lakes of the Calumet Region, very abund- 
ant in railroad ditches at South Chicago. July — October. 
The leaves of this species are quite variable, as well as the mode of 
branching. The leaves, especially on small plants, are commonly 1- 
nerved and setaceous, sometimes, particularly on larger forms, they 
are linear, bluntish, and with 3 to 5 double nerves. These forms 
usually branch but little, the leaves being arranged along the sides 
of the stems. Such forms might almost be taken for a different 
species. It is probable that the broad-leaved forms rarely perfect 
their fruit. Having first found them in 1880 at Manistee, Mich., 
they were thought to be P. flabellatus, Babington, (See Botanical 
Gazette, vol. 6, p. 262.) But the next year finding the same form 
among the Channel Islands of the St. Mary’s river, and also in the 
Calumet river, an opportunity was given to study them at home. 
None of the plants found in August had mature fruit, as was also 
the case with those at Manistee and Sault Ste. Marie. Those in the 
Calumet river were again examined in October, but with no better 
result. But these forms from the Calumet had one character, as 
yet quite distinctive of P. pectinatus, and somewhat unique among 
Potamogetons, in abundance. They were well provided with bulbs or 
tubers on the creeping, underground stem. These appear in the 
Fall, (I have detected them as early as August 23rd,) and serve to 
make the species perennial. The slender axis joining the bulbs 
usually perishes, leaving them to start a new growth in the Spring. 
Sometimes they become detached and float on the water, but 
readily sink when the water is still. They abound in starch, and 
