LAKES, RIVERS, DITCHES, ETC. 



Potamogeton fluitans. Roth. = P. natans x P. 

 lucens. As a hybrid between the two species 

 cited the characters lie between the two, the 

 blade of the upper floating leaves gradually merg- 

 ing into the leaf-stalk. This species or hybrid has 

 been found in 5 vice-counties : W. Sussex, Surrey, 

 Cambridge, Northants, and Hunts. It is also 

 found in Ireland. It is very rare, and the habitat 

 is canals. The plant is floating, and flowers in 

 June and July, and is a herbaceous perennial. 



Plantain-leaved Pondweed {Potamogeton plan- 

 tagineus, Du Croz = .P. coloratus, Hornem.). The 

 habitat of this plant is stagnant, peaty water, 

 ditches, fens. The stem is creeping below, 

 branched, with long runners from the axils. The 

 leaves are all shortly-stalked, membranous, trans- 

 parent, netted, blunt, the upper leaves opposite, 

 nearly stalkless, elliptic, or rounded, the lower 

 oblong, heart-shaped below. The stipules are 

 short, broad, and blunt. The leaf-stalk is plano- 

 convex above. The flowers are in long, cylin- 

 drical, dense spikes, on very slender equal stalks. 

 The sepals are ovate. The anther-cells are nearly 

 parallel. The fruit is green, very small, rounded 

 on the back when fresh, keeled when dry, with an 

 obsolete beak. The plant is floating, and flowers 

 between June and September, being a herbaceous 

 perennial. 



Red Pondweed (Potamogeton rufescens, Schrad. 

 = P. alpinus, Balbis). The habitat of this plant 

 is ditches, slow streams, ponds, canals. The 

 stem is simple, round in section. The leaves are 

 entire, leathery, short-stalked or stalkless, trans- 

 lucent, the lower submerged leaves stalkless, 

 tinged with red, many-nerved, lance-shaped, nar- 

 rowed both ends, netted, the upper leaves floating 

 or erect, broader, leathery, inversely ovate, blunt, 

 narrowed into a short leaf-stalk. The stipules 

 are large, blunt, not winged. The flower-stalk is 

 equal. The sepals are transversely oval. The 

 spike is stout. The drupelets are ovate, with a 

 long point, red, convex ventrally, semicircular 

 dorsally, keeled. The plant is 1-4 ft. long, flower- 

 ing between July and September, and is a herb- 

 aceous perennial. 



Various-leaved Pondweed (Potamogeton hetero- 

 phyllus, Schreb. = P. gramineus, L.). The habitat 

 of this plant is ponds, ditches, pools, and lakes. 

 The stem is much-branched below, slender, round 

 in section, green or red. The leaves are not 

 clasping, nearly flat. The submerged leaves are 

 limp, stalkless, lance-shaped, narrow both ends, 

 wavy, with small teeth, and a small blunt point. 

 The floating leaves are more or less leathery, 

 elliptic or oblong, stalked, or absent. The stipules 

 are broadly lance -shaped, blunt, with 2 stout 

 prominent ribs. The lower are linear to lance- 

 shaped, and without the ribs, equally veined, the 

 upper opposite, widely spreading. The flower-stalk 

 is thickened upwards. The fruit is blunt dorsally, 

 and, when dry, 3-ribbed, small, with a short beak. 

 The plant is 2-4 ft. in height, flowering in June 

 and July, and is a herbaceous perennial. 



Potamogeton falcatus, Fryer = /'. gramineus X P. 

 tnte>is).The habitat of this plant is fen ditches. 

 VOL. VI. 



The stem is branched from near the base. The 

 submerged leaves are stalkless, elliptic, strap- 

 shaped, not symmetrical, rounded at the base, 

 the upper leaves clasping the stems, the margin 

 entire, wavy, the floating leaves stalked, elliptic, 

 with a short, blunt point, leathery. The stipules 

 are herbaceous, persistent, the upper broad. The 

 fruit is small, ovoid, rhomboidal, with an acute 

 keel, and distinct lateral ridges. The flower- 

 stalk is thicker than the stem, hardly swollen 

 upwards, shorter than the leaves. The plant is 

 floating. It flowers in June and July, and is a 

 herbaceous perennial. 



Potamogeton lanceolatus, Sm. The habitat of 

 this plant is rivers, shallow streams, and fen 

 ditches. The stem is very slender, with few 

 branches, fragile. The submerged leaves are 

 stalkless, straight, linear, or oblong to lance- 

 shaped, entire, acute, not blunt-pointed, with a 

 chain-like network near the midrib. The floating 

 leaves are more or less leathery, elliptic to lance- 

 shaped, shortly -stalked. The stipules are awl- 

 like, the uppermost broader with 2 dorsal raised 

 ribs. The leaves are dark-green, blunt, netted, 

 or with chain-like veins all over. The flowers are 

 in a very short, ovoid spike. The flower-stalks 

 are short, not thickened upwards, slender, equal, 

 from the upper floating leaves, which are opposite. 

 The drupelets are rounded, 3 -toothed ventrally, 

 nearly straight dorsally, with a ventral beak. 

 The flowers bloom between July and September, 

 and the plant is a herbaceous perennial. 



Potamogeton mfens, Weber = ?P.g i ramtntfoli'us x 

 P. perfoliatus. The habitat of this plant is pools 

 and lakes. The plant is much-branched below, 

 the stem somewhat wavy. The submerged leaves 

 are alternate, lance-shaped, rounded below, half- 

 clasping, wavy at the border, transparent, bent- 

 back, shining. The floating leaves are leathery, 

 elliptic, stalked. The upper leaves are not always 

 leathery. The stipules are equally veined, the 

 upper ones large, persistent, nearly half as long 

 as the flower-stalk. The flower-stalk is swollen 

 upwards. The fruit is keeled when dry, with 

 3 ridges on the back. The spike is short. The 

 plant is in flower in July and August, and is a 

 herbaceous perennial. 



Potamogeton lonchites, Tuckerm. ( = F. salicifolius 

 = P. graminifolius, Fr.). The habitat of this 

 species is rivers. The stem is stout with few 

 branches, long. The submerged leaves are 

 straight, narrowly strap-shaped, stalkless, nar- 

 rowed both ends, entire, with a few parallel veins 

 next the midrib, y-g-ribbed, alternate, very long, 

 translucent. The floating leaves, when present, 

 are more or less leathery, oblong to lance-shaped, 

 elliptic, long-stalked, opposite. The stipules are 

 long, blunt, not winged. The flowers are in a 

 short spike. The flower-stalk is thickened up- 

 ward, long. The fruit is obovoid, or obliquely 

 inversely ovate, 3-keeled, with a short beak. 

 The plant is floating, flowering from June to 

 September, and is a herbaceous perennial. 



Shining Pondweed (Potamogeton lucens, L.). 

 The habitat of this pondweed is ponds, lakes, 



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