NAIADACE-T. 41 



tlic leaves variable in length, and often stalked: 1 have little doubt 

 about its being merely a variety of P. lucens. 



Long-lcavcd Pondweed. 



SPECIES XII.-POTAMOGETON PR^LONGUS. Widf. 



Plate MCCCCXI. 

 Rckh. Ic. Fl. Germ, et Helv. Vol. VII. Tab. XXXIII. Fig. 59. 



Stems stout, si^aringly branched, the lower branches barren. Leaves 

 all similar, the lower ones alternate, the upper ones opposite, sub- 

 merged, sessile and semiamplexicaul, ascending, flat, long, strapsliaped 

 or oblong-strapshaped or oblong, rounded at the base, obtuse, not 

 apiculate nor cuspidate but hooded at the apex, not serrate at the 

 margins, with 3 strong ribs and several fainter intermediate ones con- 

 nected by numerous transverse veins, and with a narrow band of 

 elongate cancellate areolation along the sides of the midrib. Stipules 

 rather large, blunt, not winged on the back, subscarious, with numerous 

 slender longitudinal fibres. Peduncles terminal and axillary, very 

 long, rather stout (but not thicker than the stem), very slightly 

 thickened towards the apex. Sepals with their lamina transversely 

 roundish-oval. Fruiting-spike dense, cylmdrical, many-flowered. Nuts 

 green, very large, not acuminated, scarcely compressed, slightly curved 

 along the upper margin, half-obovate and very sharply keeled or winged 

 beneath, termmated by a short beak forming a continuation of the 

 upper margin. Plant bright green, rarely tinged with red, retaining 

 its colour when dry, the leaves not shining. 



In deep water, in rivers and lakes. Rather scarce, but widely dis- 

 tributed on the east side of the island where it extends from .Essex 

 to Nairn. Except towards the east coast, it seems to be very scarce, 

 and its area of distribution is bounded towards the west and north- 

 west by the counties of Berks, Oxford, Stafford, Western York, 

 (Malham Tarn, Dr. J. Windsor), and Westmoreland (Mr. Borrer). 

 Very local, and rare m. Ireland, where it is confined to the west and 

 north. 



England, Scotland, Ireland. Perennial. Early Summer. 



A large species, with somewhat the habit of P. rufescens or 

 P. lucens. The leaves on the main stem are often 4 to 6 inches long, 

 those on the barren shoots smaller, all of them slightly amplexicaul, 

 and slightly hooded at the apex, never cuspidate or pointed, as in 

 P. lucens. Fruiting-peduncles 5 inches to 1 foot long, frequently 

 several together — i. e. a terminal one, and one or two axillary ones, 



VOL. IX. G 



