72 THE JOURNAL OF BOTANY 
as does Almquist in Hartman’s Skand. Fl. ed. 12, 47 (1889). 
Ascherson and Graebner (J.c.) place decipiens under two heads— 
L P. lucens x prelongus. It is possible 
that some of Dr. Tiselius’s specimens of his upsaliensis may be 
lucens X pralongus; the great majority of the specimens named 
decipiens are to me lucens x perfoliatus 
P. aupinus Balb.. (P. arte Schrad.). On the receipt of h 
sheet of specimens of this cies from the herbarium of Pro 
ata of Japan, I was rsa ae sed by the dark colour smo 
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Dr. Robbins, in Gray’s Manual, ed. 5, 486 (1879), says, “ floating 
leaves often wanting obrutus Woods).” These dark-coloured 
narrow-leaved forms are the P. rufescens ‘‘ forma angustifolia” of 
Chamisso (Linnea, he 211 (1827) = P. microstachys Wolfgang in 
Roem. & Schu ltes, Mantissa, iii. 360 (1827). 
These specimens look very corer tis from the forms named 
P. nerviger Wolfg. (l.c. 859) and those named var. maaimus Mert. 
& Koch, Deuts i i 
species. observations a orfolk, I am inclined to 
think that ea produce floating icon one year, and then not; 
but as this has not been tested by cultivation, it is better to con- 
sider it not proved. In ponds or lakes, the level of the water and 
the amoun i 
notes have been made in backwaters of rivers, or the local 
Broads, which are subject to conditions and water-level different 
from those of eg} locked ae and pee being influenced occa- 
the banks on the id flow of the tide, and large 
pamela are «didled” out and thrown in the ‘“rond.” This 
causes the Potamogetons to be cut off; they have to begin a fresh 
growth, and it is probable that in the aie in which this occurs 
many have not time to produce floating leave 
P, distinctus, sp. nov. Stems from a ae creeping rootstock ; 
when dry compressed, striated, branched. Lower leaves lanceolate 
to linear-lanceolate on petioles 14-24 in. long; secondary nerves 
(not basal) produced along the central nerve about halfway up; 
middle and upper (floating) leaves semi-coriaceous, variable in 
shape, firm, lance-linear to oblong-lanceolate, 18-18-nerved, on 
petioles 1}-6 in. long (with a mean of 243-3 in.). Pedunceles Ply 
duced often from fascicles of leaves at the apex, stout, graduall 
tapering to the base of the spike. Spikes dense, cylindrical. Frait 
with the ventral side nearly straight, the dorsal semicircular with 
three keels, the middle one subacute, undulated. the exterior ones 
