Potamogeton robbinsii
{{short description|Species of plant}}
{{speciesbox
|image = Potamogeton robbinsii NRCS-002.jpg
|genus = Potamogeton
|species = robbinsii
|authority = Oakes
}}
Potamogeton robbinsii, commonly known as Robbins' pondweed, is a North American perennial herb. The specific epithet robbinsii is named in honor of James Watson Robbins, the pioneer student of the genus.
It is found in deep to shallow, quiet, often muddy waters of lakes, ponds, and rivers.{{cite web| url=http://www.dnr.state.oh.us/dnap/Abstracts/p/potarobb/tabid/1491/Default.aspx | title=Potamogeton robbinsii | accessdate=2008-06-16}}
Description
The rootstock of Potamogeton robbinsii lacks tubers. The stems root from the lower nodes, and sterile stems are either simple or widely branching and are feather-like, covered with sheathing whitish stipules. The sterile stems measure {{convert|10-90|cm|abbr=on}} long. Flowering stems grow up to {{convert|2|m|abbr=on}} tall. Leaves on the sterile stems are linear, stiff, and grow opposite on the stem, measuring {{convert|3-8|mm|abbr=on}} long. Leaves are densely crowded on sterile stems, are auricled at their base, and have a minutely serrated margin. The tip of the fibrous pale stipule is as long or longer than its sheath. Leaves born on flowering stems are remote and reduced, with stipules with shorter tips. The branching inflorescence bears one to twenty-six straight peduncles with stiff and interrupted spikes that grow {{convert|.7-2|cm|abbr=on}} long. The plant fruits rarely, with flattened fruit that measures {{convert|4-5|mm|abbr=on}} long and {{convert|2.7-3.3|mm|abbr=on}} wide. The fruit has a prominent keel with an approximately central beak {{convert|1|mm|abbr=on}} long.{{cite book |title=Gray's Manual of Botany |author= Merrit Lyndon Fernald |year= 1970 |editor= R. C. Rollins |publisher= D. Van Nostrand Company |edition= Eighth (Centennial) - Illustrated|isbn= 0-442-22250-5 |page= 70}}
It flowers from August to September.
The plant may form dense colonies that carpet the muddy substrates of riverbottoms and lakebeds. It rarely flowers, but when it does it is very easy to identify, as it is the only Potamogeton species that has branching inflorescences.{{cite web |url= http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=222000307 |website= Flora of North America |title=Potamogeton robbinsii |access-date= 18 August 2018}}
References
{{Reflist}}
External links
- [https://web.archive.org/web/20080724061642/http://www.ecy.wa.gov/programs/wq/plants/plantid2/descriptions/potrob.html Description from Washington State Department of Ecology]
- [http://biology.burke.washington.edu/herbarium/imagecollection/taxon.php?ID=11562 Images from the Burke Museum]
{{Taxonbar|from=Q7234640}}