22. Potamogeton Obtusifolius Alert. & Koch. Blunt-Leaved Pondweed

Fig. 195

Potamogeton compressus Wahl. Fl. Suec. 1: 107. 1824.

Not L. 1753. Potamogeton obtusifolius Mert. & Koch, Deutsch. Fl.

1: 855. 1823.

Stems usually slender, compressed, widely branching, especially above. Leaves linear, 2'-3' long, 1/2 "-2" wide, obtuse, often mucronate, usually 3-nerved with a broad midrib, sometimes 5-7-nerved, 2-glandular at the base, the glands large and translucent; stipules white or scarious, many-nerved, obtuse, 6"-g" long, often as long as or longer than the internodes; peduncles numerous, 1'-1 1/2' long, slender, erect; spikes 3"-4" long, ovoid, 5-8-flowered; fruit obliquely obovoid, about 1 1/2" long and 1" thick, 3-keeled; style short, blunt, nearly facial.

In still water, Quebec to Minnesota, south to northern New York and Kansas. Also in Europe. July-Aug.

23. Potamogeton Friesii Ruprecht. Fries' Pondweed

Fig. 196

Potamogeton compressus J. E. Smith, Engl. Bot. 3: pl. 418. 1794. Not L. 1753. Potamogeton pusillus var. major Fries, Novit. Ed. 2, 48. 1828. Potamogeton Friesii Ruprecht, Beitr. Pfl. Russ. Reichs, 4: 43. 1845. Potamogeton major Morong, Mem. Torr. Club, 3: Part 2, 41. 1893. Not P. pusillus var. major M. & K. 1823.

Stems compressed, 2°-4° long, branching. Leaves 1 1/2- 2 1/2' long, about 1" wide, acute, obtuse or cuspidate at the apex, mostly 5-nerved, rarely 7-nerved, 2-glandular at the base, the glands small; stipules white, hyaline, finely nerved, obtuse or acute, 6"-12" long; peduncles 1'-1 1/2' long, often thicker than the stem and sometimes thickening upward; spikes, when developed, interrupted; fruit quite similar to that of P. pusillus, but with a recurved style, usually with a shallow pit on the sides, and with the apex of the embryo pointing toward the basal end.

In still water, New Brunswick to New York, west to North Dakota and Iowa. Also in Europe. Propagating buds occasional. July-Aug.

24. Potamogeton Rutilus Wolfg. Slender Pondweed

Fig. 197

Potamogeton rutilus Wolfg.; R. & S. Mant. 3: 362. 1827.

Stems very slender, 8 -24 long, compressed, simple or nearly so. Leaves 1' - 1 1/2' long, 1/4"-1/2" wide, acute or acuminate, strict, nearly erect, 3-5-nerved, revo-lute, the nerves prominent beneath, often 2-glandular at base and bright green; stipules acute, 6"-10" long, often longer than the internodes and hiding the bases of the leaves above, persistent, becoming white and fibrous with age peduncles 6"-18" long; spikes 3"-5" long, usually dense, but sometimes interrupted; fruit obliquely obovoid, about 1" long and i" thick, obscurely keeled or the back showing only 2 small grooves; apex of the drupelet tapering into a short facial nearly straight recurved style; embryo circle not complete, the apex pointing towards or outside the base.

Anticosti and James Bay to Michigan and Minnesota, south to New York. Also in Europe. Propagating buds usually wanting.