29 
Mississippi river bottoms at Oquawka, Ш., and sent by him to 
Prof. E. Tuckerman, who in turn transmitted it to Dr. Robbins, by 
whom it was considered as an extraordinary floating-leaved form of 
P. lucens. It has since been found by Mr. К. I. Cratty in a small 
pond at Armstrong’s Grove, Emmet county, Iowa. Both of these 
gentlemen have supplied me with numerous specimens in all stages 
of growth, from which it has been easy to deduce the characters. 
I have not seen it from any other locality, though it should be ex- 
pected in all the neighboring regions. Fruits in August. (Plate 
XXXVI.) 
13. POTAMOGETON ANGUSTIFOLIUS, Berch. and Presl, Rost. p. 19 
(1821), fide A. Bennett. 
Р. Zizi, Roth, En. Pl. Germ. i. 531 (1827). 
P. heterophyllus elongatus, M. and К. Deut. Fl. i. 845 (1823). 
P. lucens, var. heterophyllus, Fries, Nov. Ed. 2, 34 (1828). 
P. lucens var. minor, Nolte in Hans. Ех. No. 521, British Mus., 
fide A. Bennett. | 
Stem slender, branching. The branches rise from the stem at 
an acute angle, occasionally ata right angle. Floating leaves 
coriaceous or semi-coriaceous, rarely shining on the upper surface, 
elliptical, pointed or abruptly acute at the apex, sloping at base, 
the blade 1% to 4 inches long and 6 to 12 lines wide, with 13 to 
21 nerves; petioles commonly shorter than the blade, but some- 
times attaining a length of 6 inches. Submerged leaves mostly 
lanceolate or oblanceolate, occasionally oblong-spatulate, thin, pel- 
lucid, acute or cuspidate, sometimes acuminate, often wavy or crispy 
and minutely serrulate near the apex, sessile or the uppermost 
shortly petioled, 2-6 inches long and 3-15 lines wide, 7-17 nerved. 
Stipules 6-18 lines long, sometimes very broad at the base, obtuse, 
2-keeled, loose and spreading as in P. heterophyllus. 
Peduncles mostly straight and erect, stout, thicker than the 
stems, sometimes thickening upwards, 214-6 inches long. Spikes 
1-2 inches long, more in the habit of fruiting in Europe than in 
this country. Fruit obliquely obovate, 14-134 lines long and 
about 1 line wide, the face usually straight, occasionally a little 
angled, dorsally 3-keeled in the mature dried fruit; style short, 
blunt, facial; cotyledonary apex nearly touching and pointing 
directly to the end of the radicle. The fruit strongly resembles 
that of P. heterophyllus. ; 
^ 
