58 TETRAND. TETRAG. 



floating subcoriaceous ovato-lanceolate tapering into a rather 



short footstalk, lower ones long lanceolate sessile. E. B. t. 



1286. 

 HAB. In the Clyde at Dalbeth, Hopk. Ditches and lakes near For- 



far, G.Don. Fl. Aug. Sept. y. . 

 Two feet or more long. Upper leaves far less coriaceous and more 



obtuse than in the two former species. Whole plant olivaceous or 



even reddish,, beautifully veined. 



** Leaves all submersed. 



4. P. perfoliatum (perfoliate Pond-weed), leaves cordate embra- 

 cing the stem. Lightf. p. 121. E. B. t. 168. 



HAB. Rivers and lakes, very common. FL July. "If.. 

 Very distinct in the shape and insertion of the leaves. Spike on a 

 rather short peduncle, oblongo-ovate. 



5. P. densum (close-leaved Pond -weed), leaves (all) opposite 

 crowded ovato-acuminate sessile, stem forked, spike of about 

 4 flowers. Lightf. p. 122. E. B. t. 397. 



HAB. Ditches on the right hand of the walk going down the meadows, 

 near Edinb., and Corstorphine hills, Dr. Parsons. About Glasg., 

 but not common j in Bardowie Loch, Hopk. Fl. June, July. if. 



Plant rather small. Leaves much crowded upward. Spike of fructi- 

 fication very small. Peduncle very short. 



6. P. lucens (shining Pond-weed}, leaves ovato-lanceolate 

 petiolate. Lightf. p. 122. E. B. t. 376. 



HAB. Rivers and lakes, frequent. FL July. If. . 



Stems long. Leaves large, very pellucid and beautifully veined. 



Spike or spadix the longest and most crowded with flowers of any 



in the genus. 



7. P. crispum (curled Po7id-iueed), leaves lanceolate tapering 

 sessile remarkably waved serrate. Lightf. p. 122. E. B. 



HAB. Ditches and ponds, frequent. FL June, July. ")/ . 

 Stems long. Flowers rather distant on the spike. 



8. P. lanceolatum (lanceolate Pond weed), leaves linear-lan- 

 ceolate tapering at the base sessile. .E. B. t. 1985. 



HAB. Loch of Linthothen, Augus-shire, G. Don. In a mill-head 

 close by the bridge at Bervie, Kincardineshire, Maugh. 



9. P. compression (flat- stalked Pond-weed), leaves linear very 

 obtuse sessile, stem compressed, spikes about 4- flowered. 

 Lightf. p. 123. E. B. t. 418. 



HAB. Ditches and stagnant waters, but not common, Lightf. Frank- 

 field Loch, and loch near New Kilpatrick, plentifully, Hopk. FL 

 July. 7/. 



Plant small. Leaves the same width throughout. Stipules large, very 

 conspicuous, whitish. 



10. P. gramineum (grassy Pond-weed), "leaves linear-lanceo- 

 late alternate sessile broader than the stipules, stem rounded, 

 subdichotomous" (Sm.). Lightf. p. 123. E. B. t. 2253. 



