TETRANDRIA— TETRAGYNIA. Potamogelon. 233 



base of the leaf. The Jlower- stalk swells towards the top. Spike 

 2 inches long, of very numerous, crowded, greenjlowers. 

 Petiver's figure is justly commended by Haller ; but the latter quotes 

 P. serratum of Linnaeus very erroneously. Plukenet's definition, 

 of which Dillenius could make nothing, answers very well to 

 some of my specimens. 



7. P. lanceolatum. Lanceolate Pond-weed. 

 Leaves lanceolate, membranous, flat, entire ; contracted at 



the base; with chain-like reticulations near the ribs. 

 Spikes ovate, dense, of few flowers. 



P. lanceolatum. Engl. Bot.v.28. t.\985. Comp.27. Davies Welsh 

 Botanol. 18. Hook. Scot. 58. 



P. setaceum. Linn. Sp. PL 184 ? Huds. 76 ? Fl. Br. 198 ? 



P. racemosum angustifolium. Bauh. Prodr. 101? 



In Anglesey and Scotland. 



In the rivulet between Bodafon and Lligvvy, Anglesea. Rev. H. 

 Davies. Found by Mr. G. Don in the Loch of Linthothen, An- 

 gusshire ; and by Mr. Maughan in a mill-pool by the bridge at 

 Bervie, Kincardineshire. Hooker. 



Perennial. July, August. 



The whole plant, not a quarter the size of the preceding, floats 

 under water, the Jlower s always excepted, and is of a brownish 

 olive-colour. Leaves sessile, alternate except under each flower- 

 stalk, hardly 2 inches long, blunlish, even, entire, distinguished 

 by several series of beautiful, oblong, chain-like reticulations, 

 close to each side of the main rib. These unfortunately are not 

 expressed in Engl. Bot. Stipulas narrow, lanceolate, acute. 

 Floruer-stalks solitary, from the bosom of one stipula of the op- 

 posite leaves, shorter than the leaves, rather stout, each bearing 

 a small, short, dense spike, of 8 — 12 little brownish^oaers. 



This species certainly answers to the definition of the hitherto un- 

 determined P. setaceum of Linnaeus and of Hudson ; but nothing 

 can be absolutely affirmed on this subject, nor does the name 

 well agree. Some may be inclined to refer to P. lanceolatum, 

 the No. 16 of Dill, in Raii Syn. 150, quoted above under hete- 

 rophyllum. 1 have only conjectures to offer, which some au- 

 thentic specimens, if they exist at Oxford, or elsewhere, may 

 confirm or refute. 



8. P. crispum. Curled Pond-weed. Fresh- water 



Caltrops. 

 Leaves lanceolate, waved, serrated, alternate; the upper 



ones opposite. Flowers in loose spikes. 

 P. crispum. Linn. Sp. PL 182. Willd.v. 1.714. FL Br. 195. Engl. 



Bot. v. 15. t. 1012. Curt. Land. fasc. 5. t. 15. Hook. Scot. 58. 



Fl. Dan. t. 927. Br. Prodr. 343'. 



