172 86. NAIADACE^E. 



3 obscure veins. Ped. 2 3 times longer than the rather lax spike. 

 Nuts few, oblique, keeled. 



Frequent. Canals and ponds. (B) P. 6 7. Fossil marsh; Paisley Canal 

 Forth and Clyde Canal; also in many old quarry holes. 



3. P. GRAMiNEUS, Ii.Grassy Pondweed. A stronger plant 

 than the last, with broader le. , linear, obtuse, with a small point, 

 3-veined and connected by small obscure elongated reticulations. 

 Ped. scarcely longer than the ovate or oblong dense spike. Nuts 

 obovate, with a blunt keel. 



Rare. Canals and ponds. (E) P. 78. Bardowie loch ; " In the Clyde," Ure; 

 Possil marsh ; Forth and Clyde Canal. 



2. Leaves ovate or lanceolate. 



4. P. CRISPUS, L. Curly Pondweed. Stem compressed, often 

 2 3 ft. long. Le. lanceolate, waved and serrate, H to 2 in. long, 

 midrib with one slender vein on each side. Ped. elongated, bear- 

 ing 3 6 small fl. Nut with a long beak. 



Frequent. Lakes and rivers. (B) P. 6 7. River Clyde; Forth and Clyde Canal ; 

 very plentiful in the Paisley Canal. 



5. P. PERFOLIA'TUS, L. Perfoliate Pondweed. Stem round, 

 34 ft. long. Le. ovate, amplexicaul, pellucid. Ped. rather 

 thick and short. Nut rounded on the back when fresh. 



Frequent. Lakes and rivers. (B) P. 7. Paisley Canal; rivers Clyde and Cart; 

 Hogganfield loch ; Forth and Clyde Canal, <fec. 



6. P. LUCENS, "L. Shining Pondweed. A large plant. Le. 

 4 6 in. long, elliptic-lanceolate, suddenly contracted at the apex 

 into an acute or cuspidate point, margin rough or denticulate. 

 Stipules large, with 2 dorsal ivings. Ped. elongated, swelling 

 upwards. Spikes cylindrical, densely flowered. 



Common. Lakes and rivers. (E) P. 67. Plentiful in Clyde. 



7. P. NITENS, Weber. Bright Pondweed. Stems round, slen- 

 der, branched. Le. 1^ in. long, crowded on the stem, lanceolate, 

 \ amplexicaul, pellucid, margin wavy ; the upper ones broader and 

 blunt, petiole short. Stipules membranous, ^ the length of the 

 le. Ped. short and stout, thickened upwards. Fruit when dry 

 with 3 ridges on the back. (Journal of Bot., vol. ii., p. 325.) 



"Loch Ascog, Bute," Mr. G. E. Hunt. P. 8. 



B. Upper leaves floating, petiolate. 



8. P. HETEROPH^LLUS, Schreb. Various-leaved Pondweed. 

 Floating le. elliptical, petioles longer than the blade. Lower le. 

 sessile, lanceolate, tapering at both ends, denticulate, with a short 

 apiculus. Stipules strongly ribbed. Ped. thickened upwards. 

 Nut blunt on the back. 



Frequent. Ponds and ditches. (B) P. 6 7. "In Bardowie loch, east side," 

 Hopk. Rivers Clyde and Cart ; Forth and Clyde Canal, &c. 



