Hill'S Pondweed (Potamogeton hillii)
Description
The stem of this pondweed is slender and much branched, reaching up to 1 m in length. The alternate leaves are all submersed, and very narrow (0.6-2.5 mm), ranging from 2-6 cm in length. The leaves are characterized by having three parallel veins and a short bristle tip. The stipules are relatively coarse and fibrous (shredding when old) and are free from each other and the leaf stalk bases. Short (5-15 cm), curved fruiting stalks (peduncles) are terminated by globose flower/fruit clusters that arise from leaf axils or stem tips. The tiny (2-4 mm) fruits have ridges along the backside. Other narrowleaved species that lack floating leaves have either narrower leaves ( less than 0.5 mm in width, such as P. confervoides and P. bicupulatus), stipules that are attached near their bases (P. foliosus, P. pusillus), longer peduncles (1.5-4 mm) (P. friesii, P. strictifolius), or oval to cylindric flower and fruit clusters (P. pusillus, P. berchtoldii). Hill-s pondweed is further distinguished from the similar P. foliosus by its much larger fruits and bristle-tipped leaves, and vegetatively from P. strictifolius by its nodal glands (Hellquist 1987).
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Magnoliophyta
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Class: Liliopsida
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Order: Alismatales
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Family: Potamogetonaceae
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Genus: Potamogeton
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