212 POTAMOGETON. [CLASS iv. ORDER ill. 



inches in length, on footstalks about their own length ; submersed ones 

 with from three to five nerves, sessile, linear, lanceolate, waved, one to 

 two inches long, and under half an inch in breadth. Stipules under 

 water, close, lanceolate, those above strongly marked with two principal 

 ribs, broad and spreading. Peduncle swelling upwards, about three 

 times the length of the dense sgike. 



Habitat. Ponds and ditches ; not uncommon. 



Perennial; flowering in June and July. 



12. P. lanceola'tus, Sm. (Fig. 277.) lanceolate Pondweed. Leaves 

 lanceolate, tapering at the base, membranous, from five to seven 

 ribs, with transverse reticulations near the middle rib ; floating 

 ones elliptic lanceolate ; peduncle scarcely as long as the leaves ; 

 spike ovate. 



(3. without floating leaves. 



English Botany, t. 1985. English Flora, vol. i. p. 233. Lindley, 

 Synopsis, p. 250. Hooker, British Flora, vol. i. p. 77. 



Leaves alternate, except at the flower-stalks, when they are mostly in 

 pairs, sometimes more, generally under two inches in length; the upper 

 ones are filled throughout with a curious chain-like reticulation, whilst 

 in those under water it is observable only on each side the main rib. 

 Stipules narrow, lanceolate. Peduncles scarcely as long as the leaves. 

 Spike small, oval. 



This is nearly allied to the preceding, but is altogether a smaller and 

 less robust growing plant. 



Habitat. Ponds and slow streams. Anglesea, Kincardineshire ; 

 Linthothen Loch, Angusshire. /9. Found with the preceding in a rivu- 

 let in Anglesea. 



13. P. rufes'ccns, Schrad. (Fig. 278.) reddish Pondweed. Floating 

 leaves elliptic, oblong, stalked, coriaceous ; submersed ones lance- 

 olate, membranous, many-nerved, with numerous connecting veins 

 and linear reticulations. 



Hooker, British Flora, vol. i. p. 78. Lindley, Synopsis, p. 250. 

 P. rufes'ccns, English Botany, t. 1286. English Flora, vol. i. p. 231. 



There is also in this a very close affinity to the preceding species, and 

 it is not easily distinguished by any permanent and marked character. 

 It usually presents a lurid or reddish olive colour, and by this its gene- 

 ral appearance it is perhaps the most readily detected. " This does in 

 some situations much resemble P. lucens : the coriaceous floating 

 leaves are nearly as acute as the lower ones, differing only in their 

 firmer texture, and in being stalked; the ribs, shape, and size are 

 much the same in both. The lateral ribs or nerves are by no means 

 separate to the base of the leaf, but arise from various parts of the cen- 

 tral rib ; some of them one-third the length of the leaf from its base ; 

 they arc six lu seven in number on each side s two of. them more evident 



