49 
lateral keel with 6 or 8 more. Frequently the teeth are bristle- 
like, and sometimes 2-pronged. The submerged leaves are from 
14 to % line in width, rarely as narrow as in the type. The most 
distinctly-marked specimens of this form were collected by Mr. C. 
F. Parker in a pond at Rehoboth City, Delaware, August 7, 1878. 
I have since noted the following localities for it: Noank, Conn. 
(Morong); ponds on the Susquehanna and at Easton, Pa. (Por- 
ter); Florida (Curtiss, Regel, No. 72); Lower Louisiana (Langlois). 
Var. TRICHOPHYLLUs, Morong, n. var. 
About 6 inches in height, without floating leaves, the sub- 
merged leaves as fine as floss silk, and entirely destitute of nerves. 
Coll. N. L. Britton, Lake Marcia, Sussex Co. New Jersey. 
The species in pools and ponds from New England to Nebraska, 
and south to Florida and Texas, San Luis Potosi, Mexico (Schaff- 
ner Хо. 534 and Parry and Palmer No. 856). Cuba (Wright). It 
ranges farther to the south than ри Миз and not so far north. It 
occurs in Maine, but Prof. Macoun expresses a doubt whether the 
Canadian forms attributed to this species are not Spzri//us and such 
as I have seen from Canada confirm his opinion. (Plate LV.) 
32. POTAMOGETON SPIRILLUS, Tuckerm. Am. Jour. Sci. and Arts, 
2d series. vi. 228 (1848). 
P. Zetterstedtii, Wallm. ap. Sch. et Mohl. Bot. Хей. i. 256 (1843)? 
(fide Bennett Jour. Bot. xxviii. 298.) 
Stems compressed, much branched, the branches often short 
and recurved, 6-20 inches high. Floating leaves coriaceous, ob- 
tuse, usually opposite and in several pairs towards the summit of 
the stem, oval or elliptical, varying to lanceolate, the largest about 
12 lines long by 6 linés wide, sometimes narrow-oblong, deeply 
impressed beneath by 5-13-nerves.  Petiole commonly about 
equal to the blade, but sometimes only 1% or ¥ its length, some- 
what dilated. Submerged leaves linear, obtuse or abruptly acute, 
11-2 lines long and 14-74 line wide, uppermost sometimes 1 line 
wide,usually 3-nerved,the lateral nerves near the margin, rarely with 
5 very delicate nerves, often with irregular reticulated spaces on 
each side of the midrib. Stipules, like those of the preceding 
species, on the uppermost floating leaves entirely free, on the lower 
adnate to the petiole near the base, on the submerged adnate to 
MISSOURI 
BOTANICAL 
