6 
THE JOURNAL OF BOTANY 
very distinctive deep-water form is found. This—the var. lo-ngi- 
'pedunculata Merat—possesses a lengthened stem having a remarkable 
development of foliage below, few leaves above, and extremely long 
peduncles—up to inches in length. We have gathered this form 
in Ullswater, Esthwaite Water, and Derwentwater. Mr. Arth. Ben¬ 
nett informs us that the same form grows under similar conditions in 
the Great Lakes of America. 
X P. nitens Weber (P. gramineus X perfoliatus) is an extremely 
variable hvbrid locally abundant in Ullswater, Derwentwater, Win- 
dermere, and the lb. Leven, which drains it. As most of the 
P. nitens forms met with in this country greatly resemble forms of 
P. gramineus , the hybrid is commonly confused with that species. 
P. gramineus has sessile submersed leaves with a gradually tapered 
lanceolate base, serrulate margins, and an acute apex. P. nitens has 
lanceolate submersed leaves with rounded-cordate half-clasping bases. 
Occasionally, however, it possesses stem-leaves similar to those of 
P. gramineus and then presents some difficulty, but in all such cases 
the branch-leaves have + rounded bases. Immature fruits are fre¬ 
quently formed, but so far as our experience goes, mature and fertile 
fruits are not produced. 
In Pots. Brit. Isles 70, the peduncles are given as “ short and 
stout.” We often find them slender, and have specimens (teste 
J. 0. H.) from both Windermere and Ullswater possessing peduncles 
6" in length. 
P. natans L. As this species only occurs in the relatively 
shallow waters near the lake shores, ancl produces only coriaceous 
floating leaves, it presents little variation in form, and is, as nearly as 
possible, identical with the type-specimen of this species in the 
Linn. Hbm. We have seen it in Derwentwater, Bassenthwaite, 
Ullswater, Windermere, Coniston, Esthwaite W., and Loweswater. 
It also occurs in most of the smaller tarns— e.g. Elterwater and 
Blelham Tarn. We have not met with it in either Wastwater or 
Ennerdale, and only rarely in Buttermere or Crummock. 
P. polygonifoliu s Pourret. The usual form of this species—so 
generally distributed in the shallow peaty drains and ditches of the 
district—is absent from the lake-waters proper, but is replaced in 
a few of them by a deep-water form—the so-called var. pseudo- 
fluitans of Boswell Syme. In the lakes this occasionally produces a 
few thin subcoriaceous floating leaves, but normally it possesses only 
narrow elongated lanceolate leaves attenuated at the base into long 
petioles. This essentially deep-water state occurs in Wastwater and 
Buttermere—possibly also sparingly in other lakes. It may, perhaps, 
be as well, at this point, to state that we do not consider this form a 
true “variety,” but merely a “growth-form” conditioned by its 
environment, and this opinion extends to all the named “varieties” 
mentioned in this paper. A long acquaintance with plants of this 
genus growing under very varying conditions and an extended 
critical examination of their morphological differences have convinced 
us that Fryer was undoubtedly correct in stating (Pots. Brit. Isles, 
41) that “ the texture and shape of leaves are too inconstant to 
afford satisfactory grounds for varietal distinction.” 
