Naiadaceae. 147 



POTAMOGE'TON DEN'SUS (57). Opposite-leaved Pond-weed. 

 (1497) 6 — 7. Leaves translucent h — i in. ovato-cordate all opposite, stipules 

 o, stem slender forked. Ponds and streains, 



POTAMOGE'TON NA'TANS {79). Broad-leaved Pond-weed. 6—7. 

 (1479- Floating leaves 2 — 6 in. oblong olive-green, submerged leaves paler 

 1480) linear or lanceolate, stipules large, peduncles stout not enlarged up- 

 wards. Ponds and ditches. 



POTAMOGE'TON HETEROPHYL'LUS(66). Various-leaved Pond- 

 (1487) weed. 6—7. Upper floating leaves oblong sometimes absent, lower 

 submerged leaves i — 3 in. linear-lanceolate, stem slender 2 — 4 ft., 

 stipules small, peduncles stout enlarged upwards. Ponds and lakes. 



POTAMOGE'TON RUFES'CENS {62). Reddish Pond-weed. 7. 



(1483) Lower leaves submerged lanceolate, upper leaves floating obovate or 



oblong reddish, drupe red ovoid acuminate. PoJids, canals, and ditches. 



POTAMOGE'TON PECTINA'TUS (74)- Fennel-leaved Pond-weed. 

 (1505- 6 — 7. Leaves all similar submerged linear 3 — 8 in. long, stem filiform 

 1507) much-branched. Ditches and car. a!s. 



POTAMOGE'TON PUSIL'LUS (95). Small Pond-weed. 6-7. 

 (1502) Stem filiform slightly compressed, leaves 5 — 2 in. all similar linear 



narrow opaque, peduncles much longer than the few-flowered spike. 



Rivers, ponds, and ditches. 



POTAMOGE'TON CRIS'PUS (92). Curly Pond-weed. 6—7. Stem 

 (1496) slender compressed, leaves i^ — 3 in. oblong crisped slightly serrate, 

 peduncles tapering curved few- flowered. Ditches. 



Potamoge'ton praelon'gus (33). Long-stalked Pond-weed. 6—7. Leaves 



(1494) all submerged oblong 3 — 9 in. long i — i^ in. broad, peduncles long 

 stout, spike dense-flowered. [G. {Malham Tarn.) 



POTAMOGE'TON PERFOLIA'TUS {89). Perfoliate Pond-weed. 



(1495) 6 — 8. Stem stout, leaves ovato-cordate amplexicaul all submerged 

 I — 2 in., peduncles short stout, spike dense flowered. Ponds and 

 ditches. 



POTAMOGE'TON LU'CENS (73). Shining Pond-weed. 7—9. Stem 

 (1489) stout 3 — 5 ft., leaves 4 — 10 in. chiefly submerged oblong lanceolate 

 undulate, stipules large. Lakes, ponds, and streams. 



Potamoge'ton compres'sus (19). Stem compressed winged, leaves 2—8 

 (1498, 1499) in. semi-amplexicaul linear, peduncles longer than the spikes. 



[N. 



IL —ZANNICHELLIA. 



ZANNICHEL'LIA PALUS'TRIS (70). Horned Pond-weed. 5—8. 



(1 510) Leaves opposite submerged linear, flowers solitar)' minute monoecious, 



perianth o, stamen I , ovary of 4 — 6 carpels. Ponds and ditches. 



