POTAMOGETON. 371 



1. PoTAMOGETON PI, perfect. Perianth 4-parte(i. Anth. 

 4, sessile, opposite to tlie divisions of the perianth. Ovaries 

 4. Styles 0. Drupes 4, sessile. — PI. sessile, spiked. 



2. RuppiA. Fl. perfect. Perianth 0. Stam. 2, the cells 

 considerably separated; filaments very short, scalelike. 

 Ovaries 4. Styles 0. Nuta 4, with long stalks.— PI. 

 ahout 2 together. 



3. Zaito^ichellia. Fl. monoecious, axillary. Barren with 

 1 stam., and no perianth. Fertile with a bellshaped 

 perianth, persistent style, and peltate stigma. Nuts 3 — 5 

 or more, more or less stalked. 



1. PotAmoqe'ion Linn. Pondweed. 



* L, aUemate, floral I. floating and sometimes opposite; stipides 

 free. 



1. P. nutans (L.) ; 1. all stalked, upper coriaceous floating 

 ovate or elliptic folded at the base, lower leafless petioles linear 

 or setaceous, fr. (large') rounded on the back xohem fresh heeled 

 when dry, peduncle equil. — E. B. 1822. iS. vii. 50. — St. creep- 

 ing below, simple. Pefo'ofes plane-concave. L. suboordate below, 

 when pressed flat a ridge is formed on each side of the base, 



jointed to their stalks a little below the limb. Sep. stalked, roundly 

 rhomboidal. Anth.-cells not parallel. Fr. greenish, slightly 

 compressed, IJ — 2 lin. long. — Ponds, ditches, and slow streams. 



P. VI. vn. E. S. 1. 



2. P. polygonifdlim (Pourr.) ; I. all stalked, upper subcori- 

 aceous floating oblong-elliptic subcuspidate, no lec^ess petioles, 

 lower 1. linear-lanceolate, fr. minute blunt and rounded on the 

 back, peduncle equal. — P. oblongics Viv., K B. S. 2849.— St. 

 creeping below. Petioles longer than leaves, convex on both 

 sides, not jointed below the limb. Lower 1. often very narrow. 

 Spikes rather short and irregular. Sep. transversety elliptic, 

 stalked. Fr. reddish, scarcely compressed, 1 lin. long ; a faint 

 keel and lateral ridges when dry. — ^. pseudo-fluitans (Syme) ; 

 submerged 1. membranous Unear-lanceolate narrowed at both 

 ends. — ^Bitches, small streams, and ponds. 0. Buttermere. Gap 

 ofDunloe, Keny. P. VII. E.S.I. 



3. P. plantagin'eus (Ducr.) ; I. all shortly stalked membranous 

 and pellucid blunt not cuspidate nor plicate, upper elliptic, lower 

 1. oblong, _/?•. minute roimded on the back when fresh keeled when 

 dry, peduncle equal. — F. B. S. 2848. JJ. vii. 45. — St. creeping 

 below, branched, sometimes throwing out long runners from 

 its upper axils. L. all beautifully transparent and netted with 



