NAIAPACE^. 2 1 



Submerged leaves bright green, floating leaves dull green, often 

 j)urple beneath. 



In 2>onds and ditches. Common, and generally distributed in 

 l^ngland. Rather local in Scotland, where it ajjpears to be absent iroia 

 the extreme north. Common and generally distributed in Ireland. 



England, Scotland, Ireland. Perennial. Summer, Autumn. 



Rootstock extensively creeping, and sending up stems varying in 

 length according to the depth of water in which the plant grows, which 

 is rarely less than one or two feet and often greater. Submerged 

 leaves resembhng the petioles of the floatmg leaves, channeled above ; 

 floating leaves 2 to 4 inches long, differing from those of all the British 

 Potamogetons in having the coriaceous substance continued a little 

 way down the petiole, with a fold at the base, which, when the leaf is 

 pressed flat, forms a ridge on each side of the midrib. When lield 

 against the light, the transverse veins are visible, but not distinctly so, 

 on account of the thickness of the substance of the leaf. Stipules 

 scarious, those of the upper leaves very long, at length fibrous, ft-om 

 the decay of the tissue connecting their ribs. Peduncle usually about 

 as long as the spike, stout. Fruiting spike 1^ to 3 inches long. Fruit 

 nearly i inch long, when fresh greenish-ohve, obtuse on the back 

 until it dries, when a keel is developed. 



Koch and Gremer say that before flowering the submei'ged leaves 

 have a narrow lamina, which decays by the middle of May. I have 

 never seen this, though I have looked for such leaves at all seasons. 



Floating Pondweed. 



French, Fotamot nageant. German, Schivimmendes Samhrautgewachse. 



SPECIES n._POTAMOGETON POLYGONIFOLIUS. Fourret. 



Plate MCCCC. 



Eekli. Ic. Fl. Germ, et Helv. Vol. VH. Tab. XLIV. Figs. 79 and 80. 

 P. oblongus, Viv. Bah. in Engl. Bot. Sup. No. 2849. Fries, Summ. Veg. Scand. 

 pp. 68 (67), and 213. Eucli, Syn. Fl. Germ, ct Helv. ed. ii. p. 775. 



Stems round, simple or nearly so. Lower leaves alternate, submerged, 

 shortly stalked, oblanceolate or elliptical or strapshaped-elliptical and 

 membranous — or longly-stalked, subcoriaceous, rising out of the w^ater, 

 and oblong-ovate or oval ; uppermost leaves opposite, floating or rising 

 out of the Avater, of the same texture as the whole of the rather short 

 petiole, oval or oblong or elliptical, subcoriaceous, -^vith nmnerous longi- 

 tudinal ribs connected by cross veins, which are very conspicuous if the 

 tbied leaf be held against the light, when minute areolation is scarcely 

 perceptible all over the leaf between the veins. Stipules large, not 

 wuiged on the back, subfibro-scarious. Peduncles axillary, slender, 



E 2 



