ON A NEW BRITISH POTAMOGETON OF THE NITENS GROUP. 291 
have the minutely serrulate leaf-edges of P. undulatus, and to be 
specifically identical with that t form; as a variety of undulatus, it 
iffer - Cooperi in its nearer approach to P. perfoliatus, in 
its peel gents leaves, and in its less mnitens-like facies generally. 
On the other hand, P. undulatus y. Cooperi has strongly and 
ene recurved leaves in many of its states, the leaves are more 
undulate, and the whole — t more nearly approaches both P. 
nitens wan P. crispus in facie 
, then, w n See with a group of closely similar forms, 
which, although slightly, and petoonae! constantly, differing from 
e another, constitute a very natural “species” of equal — 
on 
with such aggregates as P. ao and P. decipiens. The 
species again form a natural larger group, the members of gis 
seem to have had one common descent from P. perfoliatus on one 
side or Ars 
Placed in natural sequence, according to their degrees of 
Saudia hlasibe to the type first described by Wolfgang, the undulatus 
forms will stand as— 
P. unputatus Wolfg. 
var. a. Coopert 
var. b. Jacksoni. 
The typical P. undulatus has been variously referred by good 
botanists to P. crispus, P wtih and P. prelongus; var. Jacksoni 
to P. perfoliatus, P. nitens, and more doubtfll to P. prelongus ; 
and var. i abs to P. crispus and P. perfolia 
of. Babington’s opinion on var. Tocca is so valuable that I 
cannot Stain from quoting it:—‘‘I am not clear about this; can 
it be P. nitens? or is it a state of P. prelongus? I think the former ” 
(Record Club Report, 1880, P. 150). Here the Professor shows that 
grasp of this difficult genus which has made the descriptions 2 
Potamogeton in his Hesse of British Eaiabe the clearest and mo 
accurate we hee pos 
In & 
resent species :—‘ In deep water, as in the Kyle of Sutherlan 
the Lossie, and other places, a form occurs with the leaves much 
than usual, less amplexicaul, darker in colour, and 
turning black and dim £ rm should be ed 
his form 
in a fresh state, to see whether it has a compressed stem. Also all 
forms of perfoliatus with semiamplexicaul narrowly elongate leaves 
should be carefully compared with typical examples of the species ; 
if the faint int stcodiate ribs do pe oe four on the whole leaf, 
then the plant eee a bly be P. 
M. e to Mr. E. F. Oona and to Mr. C. R. Billups 
for an iaistianse of Fee specimens, and for _ on the habit of 
P. Coopert in its native localities; and also to Mr. R. Morgan for 
the great pains he has tak te Ww the & accompanying plate, 
which exactly fieittinciste : series of fresh specimens gathered by 
Mr. Cooper in the Loughborough Canal. No space could be 
afforded to figure the earlier states of the plant, Salk often so 
little resemble the figures here given as to look like a distinct 
u2 
