Potamogeton robbinsii

Oakes

Magazine of horticulture, botany and all useful discoveries and improvements in rural affairs 7: 180. 1841.

Common names: Robbins' pondweed fern pondweed potamot de Robbins
IllustratedEndemic
Treatment appears in FNA Volume 22.

Rhizomes present. Cauline stems terete, without spots, to 100 cm; glands absent. Turions absent. Leaves submersed, conspicuously 2-ranked, sessile, stiffish; stipules persistent, conspicuous, adnate to base of blade about ¼ length of stipule, connate, greenish brown to white, ligulate, 0.5–2 cm, fibrous, shredding at tip, apex obtuse; blade dark green to reddish green, linear to lanceolate, not arcuate, 2–7 (–12) cm × 3–4 (–8) mm, base rounded, with basal lobes, not clasping, margins minutely spinulose to serrulate, not crispate, apex not hoodlike, acute, lacunae absent; veins 20–60, fine. Inflorescences often branched; peduncles not dimorphic, axillary, erect, cylindric, 3–5 (–7) cm; spikes not dimorphic, moniliform (i.e., beaded), 7–20 mm. Fruits stipitate, brown, obliquely obovoid, turgid, abaxially and laterally keeled, 3–4 (–5) × 2 (–3.3) mm, lateral keels without points; beak erect, recurved at apex, 0.7–0.9 mm; sides without basal tubercles; embryo with less than 1 full spiral. 2n = 52.


Phenology: Flowering late summer–early fall.
Habitat: Shallow to deep water of ponds, lakes, and slow-flowing rivers
Elevation: 0–3000 m

Distribution

V22 183-distribution-map.jpg

Alta., B.C., Man., N.B., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Ala., Alaska, Calif., Conn., Idaho, Ill., Ind., Maine, Mass., Mich., Minn., Mont., N.H., N.J., N.Y., Ohio, Oreg., Pa., R.I., Utah, Vt., Wash., Wis., Wyo.

Discussion

Potamogeton robbinsii is our most easily recognized species when it is fertile. It is the only species with branched inflorescences. The species, however, occurs in fairly deep water, forming large colonies that essentially cover the substrate. Only rarely do the plants flower. It also is the only species with truly auriculate leaves, the blades forming small lobes projecting past the stem on each side of the stem. Leaf blades of other Potamogeton species may have slightly rounded bases, but no others have lobes that actually protrude past the stem.

The species has a fairly large disjunction; primarily known from the northern part of the flora, it also occurs in the Tensas River area, Baldwin County, Alabama. The Alabama population has been collected on at least two occasions over 40 years, once as recently as 1970.

Selected References

None.

Lower Taxa

None.

"shortened" is not a number."shortened" is not a number."not elongating" is not a number."connate" is not a number.

... more about "Potamogeton robbinsii"
Acute (?) +, Not hoodlike (?) +  and Obtuse (?) +
Robert R. Haynes +  and C. Barre Hellquist +
rounded +
recurved +  and erect +
0.07 cm0.7 mm <br />7.0e-4 m <br /> (0.09 cm0.9 mm <br />9.0e-4 m <br />) +
7 cm70 mm <br />0.07 m <br /> (12 cm120 mm <br />0.12 m <br />) +
0.4 cm4 mm <br />0.004 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
dark green +  and reddish green +
2 cm20 mm <br />0.02 m <br /> (7 cm70 mm <br />0.07 m <br />) +
linear;lanceolate +
3mm;4mm +
0 cm0 mm <br />0 m <br /> (100 cm1,000 mm <br />1 m <br />) +
Robbins' pondweed +, fern pondweed +  and potamot de Robbins +
Alta. +, B.C. +, Man. +, N.B. +, N.W.T. +, N.S. +, Nunavut +, Ont. +, P.E.I. +, Que. +, Sask. +, Ala. +, Alaska +, Calif. +, Conn. +, Idaho +, Ill. +, Ind. +, Maine +, Mass. +, Mich. +, Minn. +, Mont. +, N.H. +, N.J. +, N.Y. +, Ohio +, Oreg. +, Pa. +, R.I. +, Utah +, Vt. +, Wash. +, Wis. +  and Wyo. +
0–3000 m +
0.4 cm4 mm <br />0.004 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.33 cm3.3 mm <br />0.0033 m <br />) +
keeled +, turgid +  and obovoid +
2 cm20 mm <br />0.02 m <br /> (?) +
Shallow to deep water of ponds, lakes, and slow-flowing rivers +
emersed +  and submersed +
axillary +  and terminal +
cylindric +  and capitate +
not crispate +
spinulose to serrulate +
orthotropous +
not pedunculate +
emersed +  and submersed +
cylindric +  and capitate +
not spiraling +
5 cm50 mm <br />0.05 m <br /> (7 cm70 mm <br />0.07 m <br />) +
not dimorphic +
cylindric +
3 cm30 mm <br />0.03 m <br /> (5 cm50 mm <br />0.05 m <br />) +
Flowering late summer–early fall. +
short-stipitate +  and stipitate +
4 +  and 1 +
Magazine of horticulture, botany and all useful discoveries and improvements in rural affairs +
auriculate +  and not auriculate +
not persisting +
Illustrated +  and Endemic +
not dimorphic +
emersed +  and submersed +
moniliform +
0.7 cm7 mm <br />0.007 m <br /> (2 cm20 mm <br />0.02 m <br />) +
epitepalous +
compressed;terete +
greenish brown +  and white +
0.5 cm5 mm <br />0.005 m <br /> (2 cm20 mm <br />0.02 m <br />) +
Potamogeton robbinsii +
Potamogeton +
species +
20 +  and 60 +
caulescent +, not rhizomatous +  and rhizomatous +
annual +  and perennial +