232 TETRANDRIA— TETRAGYNIA. Potamogeton. 



long, all nearly alike, more or less acute, tipped with a small 

 point ; their colour olive green, now and then reddish in the 

 upper ones ; their base usually tapering into the footstalk^ some- 

 times rounded 3 their margins more or less undulated, becoming 

 plaited when pressed, and the edge is rough, or very finely cre- 

 nate, but this last character varies. What is most characteristic 

 is the strong network, formed by the numerous transverse veins, 

 connecting the 5 or 7 longitudinal ribs : and especially the union 

 of the side ribs to the middle one, a considerable way above the 

 base of the leaf. The Jlowers talk swells towards the top. Spike 

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

 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 tp 

 some of my specimens. 



7. P. lanceolatmn. 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. EngLBot.v.1%.t.\%%o. Comp.27. Davies Welsh 



Botanol. \S. Hook. Scot. dS. 

 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 Lligwy, 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 powers always excepted, and is of a brownish 

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

 stalk, hardly 2 inches long, bluntish, 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 narrov/, lanceolate, acute. 

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

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

 a small, sl^rt, dense spike, of 8 — 12 little brownish^oiyer^. 



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 Rati Syn. 150, quoted above under hete- 

 rophyllum. I have only conjectures to offer_, which some au-. 



