﻿98 P0TAM0GET0N POLYGONIFOIJUS VAR. PSEUDO-FDUITANS. 



soon decaying, short, clasping ; upper patent, acute, 1| in. long. 

 Colour of the whole plant greenish brown, upper leaves darker. 



This description, excepting the variable proportions of length and 

 breadth of leaves, would serve for many of the deep-water forms of 

 P. pnlijij mifolius; and if we turn to Dr. Syme's original description in 

 English Botany, ed. iii. (1869), and compare it with the specimens 

 above described, we find a sufficient specific correspondence :— 

 " Var. /?. pseudo-fluitans. Lower leaves membranous, elliptical, 

 Btrap-shaped, attenuated at each end; floating leaves subeori- 

 aceous, gradually attenuating into the petiole " (I. c. p. 28). From 

 this description I think it is clear that we need not limit the varietal 

 name of pseudo-fluitans too strictly, but give it as wide an applica- 

 tion as we do to his vars. a. and y. 



Before pointing out the differences between the plant from the 

 Eiver Leven and P. fluitans of Both, I think it will be well to ask 

 botanists who have studied the living forms of P. polygoni/qlim 

 whether it is probable that any of them are more than states due to 

 local conditions, and whether they do not pass from one state to 

 another under changed conditions of growth ? Unfortunately, P. 

 polygonifolius is almost absent from the Eastern Counties, and I 

 have only once seen it growing wild, on Dersingham Heath, West 

 Norfolk. That was the var. y . ericetorum of Syme. In default 

 of original observations I gladly quote a passage from the Flora 

 of Oxfordshire:—" The plant is the heath form P. vri-u»m,n Syme. 

 In 1885 I noticed the floating form in a small pond near the brick- 

 yards, which now probably occupy the old station, and a month 

 later, then being dried up, the plant assumed the heath form " {I. c. 

 p.. 888). A clear statement like this, by so careful a botanist as 

 Mr. Druce, seems to me conclusive that vars. «. and y. are merely 

 states, not true varieties ; and I cannot help thinking that var. (i. 

 is only a state of var. «. growing in running water. 



Although I have not been able to collect P. polygonifolius myself, 

 I have had many forms of it sent me to cultivate, and I have not 

 found any of these forms permanent under cultivation at present. 

 This, however, is no proof that permanent forms do not exist ; all 

 We can safely accept at present is the change of var «. into var. y. 



Potamogeton fluitans is separated from P. polygonifolius var. 

 pseudo-fluitans by the peduncles being thickened towards the upper 

 part by the barren spike, and by the lateral ribs being sunk in the 

 substance of the leaf on the under side ; while in pseudo-fluitans the 

 peduncles are equal in thickness thoughout, the spikes appear to be 

 fertile, and the ribs are prominent on the under side of the lamina. 

 There are other differences in habit and in the lower leaves and 

 stipules which I do not dwell upon here, because of the insufficiency 

 in number and perfection of the specimens of pseudo-fluitans available 

 for comparison. 



I am not inclined to regard pseudo-fluitans as a northern form of 

 polygonifolius, because I have seen specimens, collected at Gam- 

 lingay in Cambridgeshire, which seem to me to belong to the 

 variety as defined by Syme. In my herbarium there is a specimen 

 collected by the late Abram Sturrock, but unnamed by him, 



