48 
31. POTAMOGETON DIVERSIFOLIUS, Raf. Med. Repos. 2d Hex. v. 
354 (1808). 
P. hybridus, Mx. Fl. i. 101 (1803). 
We are obliged to drop the name of Michaux, because it had 
been previously employed by Thuillier for P. heterophyllus (Fl. Par. 
1790), and that of Rafinesque comes next in date. 
Stems flattened, sometimes terete, much-branched, but never 
recurved as sometimes occurs in P. Spirillus. Floating leaves 
coriaceous, the largest 12 lines long by 6 lines wide, oval, ellipti- 
cal and obtuse or lance-oblong and acute. Petioles generally 
shorter, but sometimes longer than the blades, filiform or dilated. 
Submerged leaves setaceous, flat, in the typical form seldom over 
М line in width, 1-3 inches long, I-nerved, often with many fine 
lines and long reticulations on each side of the midrib. Stipules 
obtuse or truncate, hyaline, 3-5 lines in length, on the floating leaves 
free, on the submerged leaves commonly adnate to the petiole, but 
often free. Emersed peduncles 3-7 lineslongand thickened upwards. 
Submerged peduncles 2-3 lines long, as long as the spikes, clavate, 
often recurved. Emersed spikes 3-5 lines long, occasionally inter- 
rupted. Fruit rarely over % line long and nearly as broad, 3- 
keeled, middle keel narrowly winged, usually with 7 or 8 knob-like 
teeth on the margin, the lateral keels sharp or sometimes rounded ; 
style quite apparent as a short point, apical; embryo coiled 1 Y 
times. This and the following species are much alike in general 
appearance and often confounded. In well-marked forms, how- 
ever, the two may readily be distinguished not only by the differ- 
ence in the submerged peduncles, but by the width of the 
submerged leaves, those of P. diversifolius being capillary or 
setaceous and only I-nerved. Sometimes the leaves are broader, 
and then the chief mark of distinction lies in the submerged pe- 
duncles. Both species are really intermediate between the section 
of Potamogetons with free stipules and that with adnate stipules, 
as in the uppermost leaves the stipules are free, and adnate only 
in the lower. In extent of adnation this species approaches the 
former and the following species the latter. 
Var. MULTI-DENTICULATUS, Morong, n. var. 
Varies from the type in the numerous teeth on the fruit, as 
many as 12 being sometimes found on the middle keel, and each 
