rOTAMOGETON. 
443 
slender, a little thickened below the joinings ; branches fascicu- 
late. L. not transversely veined. Floral stip. large. Ped. not 
thickened. Sep. roundish, stalked. Fr. often warted on the 
back and with a tubercle on each side at its base when fresh. 
— Norf. SuflF. Camb. Devon. Surrey. P. VII. VIII. E. 
**** L. all submersed, alternate, linear, sheathing. 
28. P. flahelldtns (Bab.) ; lower I. broadly linear abruptly 
apiculate or acuminate 3 — b-veinedyt 'iih transverse veins, uiyptr 
I. narrow acute 3-veined, fr. (2 lin. long) broadly i-obovate 
inner edge nearly straight but gibbous near the top rounded on 
the back, nut with a prominent keel. — Sy.E.B. 1421. Phytol.'w. 
1158. — Rhizome spreading, from a tuber that has outlived the 
winter. Floating st. branched, wavy, spreading like a fan. 
Broad 1. usually decayed at the time of flowering. 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 nut with faint lateral ridges, [a slender maritime 
form with setaceous 1. is var. scoparius (Fryer).] Pouds and ditcheS 
chiefly near the sea. B. VI. VII. E. I. 
29. P. pectindtus (L. em. Bab.); I. formed of 2 interrupted 
tubes, lower narrowly linear flattened slightly grooved above, 
upper setaceous, fr. (2 lin. long) broadly i-obovate inner edge 
rather convex rounded on the back, nut with 2 lateral ridges 
but (usually) no heel. — E. B. 323. — St. branched, forming linear 
masses. L. very gradually acute, all 1 -veined, no marginal 
veins and scarcely thickened there ; upper 1. with an oval 
section. Spikes slightly interrupted. Baok 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. 
30. P. marinus (L. sec. Fr.) ; I. linear-setaceous 1-veined with 
transverse veins, S2nkes greatly interrupted, fr. (li lin.) obovate 
rugose rounded on the back without keel or ridges when dry, nut 
round-backed. P.filiformis (Pers.). — Sy. E. B. 1424. — L. like 
those of the preceding but longer. Fr. smaller. Whorls very 
distant on the spikes. Peduncles very long. — Lakes, rare. 
P. VI. VII. ■ E. S. I. 
***** L. all opposite, submersed ; stip^des none. 
31. P. den'sus (L. em. Cham. & Schlecht.) ; I. all opjjosite 
pellucid clasping elliptic-lanceolate or lanceolate, spikes shortly 
stalked ultimately reflexed.— i?. B. 397. B. vii. t. 28.— L. 
crowded, rather recurved. Spike 4-flowered. Sep. triangular. 
—Ditches. P. VL VII. E. S. L 
