CLASS IV. ORDER III. J POTAMOGETON. 209 



4. P. gramine'us, Linn. (Fig. 268.) grassy Pondweed. Leaves 

 broadly linear, obtuse, three-nerved, lateral veins slender, obscure; 

 peduncle from the axils of the leaves, scarcely longer than the 

 oval spike. 



English Botany, t. 2253. English Flora, vol. i. p. 235. Hooker, 

 British Flora, vol. i. p. 75. P. oltusifo'lius, Lindley, Synopsis, p. 249. 



Stem slender, wavy, more or less branched, especially near the upper 

 part. Leaves about three inches long, crowded, spreading, alternate, 

 except at the extremity, where they are generally opposite, linear, but 

 gradually contracted towards the base. The main rib is accompanied 

 by numerous lateral, parallel, obscure reticulations, with the two outer 

 veins solitary, very slender, sometimes scarcely visible. Stipules nar- 

 rower than the leaves. Peduncles invariably axillary. Spikes equal 

 in length to the peduncle, which is very short, oval, close, rising above 

 the surface of the water. 



The characters founded on the veins of the leaves of this species, are 

 remarkably constant. 



Habitat. Ponds, ditches, and slow streams. Norwich; Deptford; 

 Lancashire ; Beverley, Yorkshire. 



Perennial ; flowering in July. 



5. P. acutifo'lius, Link. (Fig. 269.) sharp-leaved Pondweed. Leaves 

 linear, acuminate, three-nerved, with numerous intermediate pa- 

 rallel veins running throughout the whole surface ; spikes com- 

 pact, oval, the length of the short peduncle. 



Hooker, in English Botany, Supplement, t. 2609. 



This and the following species are well distinguished by the many 

 close and parallel nerves. 



Habitat. Ponds and ditches. About Amberley, Henrield, and 

 Lewes, Sussex. 



Perennial ; flowering in July. 



6. P. zosteratfo'lius, Schum. (Fig. 270.) Grass-wrack-like Pondweed. 

 Leaves broadly linear, with an oblique acuminate point, three 

 principal nerves, with numerous intermediate ones, occupying the 

 whole surface; stem compressed; peduncles long; spikes cylin- 

 drical. 



Hooker, British Flora, vol. i. p. 76. Lindley, Synopsis, p. 249. 

 P. cuspida'tus, English Flora, vol. i. p. 235. 



Leaves intersected into three equal portions by the principal veins, 

 which, as well as the intermediate ones, are distinct 



Sir James Smith says this has often been confounded with P. com- 

 pressum, but is more robust and of larger growth than that species ; 

 and adds, that Professor Schrader had communicated it to him as the 

 P. cuspidatum of his Flora Germanica, and this name Sir James had 

 also adopted. 



VOL. i. 2 E 



