Potamogeton oakesianus

Rhizomes present. Cauline stems terete, with red spots, 7--75 cm; nodal glands absent. Turions absent. Leaves both submersed and floating, ± spirally arranged. Submersed leaves sessile, lax; stipules persistent, conspicuous, convolute, free from blade, whitish, not ligulate, 1--3 cm, delicately fibrous, not shredding at tip, apex obtuse; blade pale green, linear to phyllodial, not arcuate, 5--16 cm ´ (0.25--)0.3--1 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex acute, not hoodlike, lacunae absent, setaceous; veins 3. Floating leaves: petioles continuous in color to apex, 3.2--7.5 cm; blade adaxially light to dark green, lanceolate to elliptic or ovate, (1.5--)2--4(--5.5) cm ´ 10--20(--30) mm, base rounded or tapering, apex acute; veins (7--)9--19(--23). Inflorescences unbranched, emersed; peduncles not dimorphic, terminal, ascending to spreading, cylindric, 2.5--8 cm; spikes not dimorphic, cylindric, 10--35 mm. Fruits sessile, greenish brown, obovoid, turgid, abaxially keeled, laterally keeled, 2.5--3.5(--3.7) ´ (1.6--)2--2.4 mm, lateral keels without points; beak erect, 0.4--0.8 mm; sides without basal tubercles; embryo with 1 full spiral. Chromosome number apparently unknown.

Flowering summer--fall. Quiet acidic waters of bogs, ponds, and lakes; 50--1500 m; St. Pierre and Miquelon; B.C., N.B., Nfld. and Labr., N.S., Ont., Que.; Conn., Maine, Mass., Mich., Minn., Mont., N.H., N.J., N.Y., Pa., R.I., Vt., Va., W.Va., Wis.

Potamogeton oakesianus, along with Potamogeton floridanus and P. natans, has floating leaves and phyllodial submersed leaves. The petioles of this species and of P. floridanus lack a short area of light-colored tissue immediately proximal to the blade.

Much like no. 23 [Potamogeton natans L.]; stem to 1 m, often freely branched; submersed lvs petiole-like but very delicate, 0.25-1 mm wide, with 3 veins; floating lvs lanceolate to elliptic or ovate, 2.5-6 נ1-2.5 cm, the broader ones obtuse; stipules 2.5-4 cm; peduncles 3-8 cm, conspicuously thicker than the stem; spike 1.5-3 cm; frs obovoid, 2-3.5 mm, with a tight, dull pericarp, not pitted or wrinkled. In quiet, acid waters; Nf. and Que. to N.J., Pa., and Wis.; rep. from W.Va.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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