Oakes' Pondweed

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.

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.

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.

Flowering summer--fall.

Quiet acidic waters of bogs, ponds, and lakes; 50--1500m.

Potamogeton oakesianus Robb. in A. Gray, Man. ed. 5. 485. 1867
1 Potamogeton Purshii Tuckerm. Am. Jour. Sci. II. 6: 228. 1848.
Stem sometimes much branched ; floating leaves petioled ; blades coriaceous, revolute, elliptic-lanceolate or ovate-lanceolate, acute at the apex, and acute, or rounded and subcordate, at the base, 3.2-4.9 cm. long, 1-2.8 cm. wide petioles mostly 2-3 times aslong as the leaf -blades or shorter ; stipules acute, 2.5-4 cm. long, axillary and free from the petioles ; submerged leaves reduced to phyllodia, terete, scarcely 1.5 mm. thick and often greatly elongated; spikes cylindric, 2-3.1 cm, long; peduncles 3-6 cm. long, twice thicker than the petioles ; nutlets smooth on both sides, 3-keeled on the back ; embryo an incomplete spiral, the apex pointing towards the base.
Type locality : Eastern Massachusetts.
Distribution : Maine to Wisconsin, south to New Jersey.