NOTES ON PONDWEEDs. 807 
seasons ; still, as they are annually produced to some extent, they 
may be subjected to the continuous and patient observation which 
the accurate solution of problems in Natural History demands. 
The species which grow in the fens, and which form the subject 
of this note, are P. natans, P. fluitans, P. plantagineus, P. hetero- 
phyllus and its allied forms P. varians and P. nitens? (an undescribed 
r 
feet deep; the rest are, as far as the recognised species go, in- 
habitants of both deep and shallow water alike. 
y 1-12th in. broad; upper leaves oval to suborbicular, petiole 
$-1} in. long, lamina 14-24 in. long by 1-2 in. broad. As P. 
water. 
P. fluitans Roth.—The land-form of this plant is clearly distinet 
from P. natans on the one hand, and P. Zizii on the other_—the two 
species which fluitans most closely resembles in its perfect state. 
The lower leaves are reduced to two or three, narrowly linear 
1-12th in. broad by 2-8 in. 1 } 
** phyllodes” of P. natans, or of P. Zizii, as they occur in the - 
orm 
f of those species; the upper leaves spring from an erect 
unbranched stem 1-2 i ,—like of the land-form of P. 
Zizii, only much dwarfer and more slender,—pe : 
this mode of existence. From the resemblance of the two species 
in their ordinary state it will probably continue to grow on 
of P. natans. It is quite distinct from any land-form known to me, 
althouch it, hag certain faial bl : p mnt ae a 
