Potamogeton hillii Morong

Potamogeton hillii is an easily recognized species either in fruit or when sterile. The leaf blade has a bristle tip and five or fewer veins. Those characters combined with the usual absence of nodal glands will separate this species from all other North American linear-leaved species. Ecologically, it is consistently found in more alkaline waters than any other North American pondweed. A study of 35 localities established the mean to be 124.1 mg/l CaCO3 (C. B. Hellquist 1984).

Rhizomes absent. Cauline stems slightly compressed, without spots, 30--60 cm; glands rare, when present, brown to green, 0.1--0.3 mm diam. Turions terminal, rare, 2.8--3 cm ´ 1.5--3 mm, soft; leaves ± 2-ranked; outer leaves 3--4 per side, base not corrugate, apex acute to apiculate; inner leaves undifferentiated. Leaves submersed, ± spirally arranged, sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, white to light brown, not ligulate, 0.7--1.6 cm, slightly fibrous, rarely shredding at tip, apex obtuse; blade pale green to olive-green, linear, not arcuate, 2--6 cm ´ 0.6--2.5(--4) mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, apiculate to bristle-tipped or rarely blunt, lacunae in 1--2 rows each side of midrib; veins 3. Inflorescences unbranched, emersed; peduncles not dimorphic, axillary and/or terminal, erect to ascending, rarely recurved, slightly clavate, 6--13.5 mm; spikes not dimorphic, globose, (2--) 4--7 mm. Fruits brown to light greenish brown, ovoid to orbicular, turgid, sessile, abaxially and laterally keeled (3-keeled), 2.3--4 ´ 2--3.2 mm, lateral keels without points; beak erect, 0.3--0.7 mm; sides without basal tubercles; embryo with 1 full spiral. Chromosome number unknownnot available.

Ont.; Conn., Mass., Mich., N.Y., Ohio, Pa., Vt., Va., Wis.

Flowering and fruiting summer.

Alkaline waters of marshes, ponds, lakes, and slow-moving streams; 50--400m.

Potamogeton porteri Fernald

Potamogeton hillii Morong, Bot. Gaz. 6 : 290. 1881
Stem slender, branched, without propagating buds ; leaves all submerged, linear, acute, cuspidate or aristate at the apex, 2.5-6 cm. long, 2-2.8 mm. wide, with 2 glands at the base or glandless, 3-nerved, the lateral nerves less prominent than the midrib and remote from it; stipules scarious, 0.6-1.8 cm. long, aristate or rarely obtuse at the apex, axillary and free from the leaf-bases ; spikes few-flowered; peduncles scarcely more than 1.5 cm. long, as thick as or a little thicker than the stem ; nutlets smooth, 3-keeled, the middle keel prominent and undulate or crisped, the lateral keels inconspicuous ; style projecting at least 1 mm. from the body of the fruit and crowned with a depressed-globose stigma; embryo a complete spiral, the curved apex pointing inside the base.
Type locality : New York and Michigan.
Distribution : New York to Michigan and I,ake Superior, south to Pennsylvania and Missouri.

Potamogeton hillii, common name Hill's pondweed, is a species of plant found in North America. It is listed as endangered in Connecticut, Ohio, and Pennsylvania. It is listed as a special concern in Massachusetts and as threatened in Michigan and New York (state).

Potamogeton hillii là một loài thực vật có hoa trong họ Potamogetonaceae. Loài này được Morong miêu tả khoa học đầu tiên năm 1881.