366 94. POTAMOGETONACEiE. 



roimdisli, stalked. Moriandroug. Fr. often warted on the back 

 and "with, a tubercle on each side at its base when fresh. — About 

 Norwich. P. VII. VIII. > ,: E. 



**** li. all submersed, alternate, linear, sheathing. 



21. P. Jlahelldttis (Bab.) ; lowei', I. broadly linear abruptly 

 apiculate or acuminate S—5-veineil with transverse veihSj^oai- 

 incf I. narrow acute S-veincd, fr. (2 lin. long) broadly J-obovate 

 inner edge nearly straight hut gibbous near the top rounded on 

 the back, nut with a prominent keel.— P/jyfe)?. iv. 1158. P. zos- 

 teraceus Bab. (not Fr.). — Rhizome spreading, fi-om a tuber that 

 has outlived the winter. Floating st branched, spreading like 

 a fan. Broad lower 1. usually decayed at the time of tlowering. 

 Lateral veins of upper 1. at the margin, of lower 1. distant from 

 it. Spikes slightly interrupted. Back of fr. without- ridges, 

 rounded when fresh ; enclosed mit with'faint lateral ridges. — 

 Ponds and ditches near the, sea. P. VI. VII. E.I. 



22. P. pectindtiis (L.) ; Informed of 2 interrupted tnbes, lower 

 narrowly linear flattened slightly gi'ooved above, upper setaceotis, 

 fr. (2 lin. long) broadly j-obovate inner edge rather convex 

 rounded on the back, nut zoith 2 lateral ridges Tntt (usually) no 

 heel. — E. B. 323. M. yii. 19. — St. branched, forming linear 

 masses. L. very gradually acute, all 1-veined, no marginal veins 

 and scarcely thickelied there; upper 1. with an oval section. 

 Spikes slightly interrupted. Back of fr. without ridges and 

 rounded when fresh ; nut with strong lateral ridges, varying 

 greatly in length and size of st. and leaves. — Ponds and streams. 

 P. VI. VII. ' E.S.I. 



28. P. filifor'mis (Nolte !) ; I. linear-setaceous 1-veined with 

 transverse veins, spikes greatly intemtpted,fr. (IJ lin.) obovate 

 rugose rounded On the hach VMhbut heel or ridges when dry, nut 

 round-backed. — L. like those of the preceding but longer. Fr. 

 smaller. Whorls very distant on the spikes. Peduncles very 

 long. — ^Eare. In Scotland. Lough Cullen and Lough Coim, 

 Mayo: P.VLVIL S. L 



***** L. all opposite, Mibmersed; stipules none. 



24. P. den'sus (L.) ; l.all opposite pellucid clasping elliptic- 

 lanceolate or lanceolate, spikes shortly stalked mtiniately re- 

 flexed.—^. P. 397. P. vii. t. 28. — L. crowded, rather recurved. 

 Spike 4-flowered. Sep. triangular. — Ditches. P. VI. VII. 



E. S. L 



2. Etjp'pia Linn. Tassel-Pondweed. 



1. R. marit'ima (L.); common ped. long spiraUy ttoisted, «a\h..- 

 cells oblong 1 5 times as. long as broad, nut ovoid rather ob- 



