West Highland Flora

Fennel-leaved Pondweed


Potamogeton pectinatus

 

Potamogeton pectinatus

Photo Carl Farmer
6 Aug 2003 Dunvegan, Skye

Uncommon, in lochs

Leaves c 5-20 cm long, c 0.25-1.5 mm wide.  Fruit c 3-5 mm long, 2-4 mm wide.

ID: Stipules in two parts, first joined to the leaf and forming a sheath, then at the top of this sheath a projecting ligule.  The effect is rather like that of a grass leaf with its sheath and ligule.  To distinguish from Slender-leaved Pondweed fruits are necessary.  In the present species they have one side almost flat and the other very rounded, so that the beak of the fruit is well over to one side (see bottom left pic).  In Slender-leaved both sides are rounded and the beak is almost in the centre, also the fruit is smaller, no more than 3 mm tall and 2 mm wide.

Other features: This species and Slender-leaved Pondweed form a group different from the other pondweeds in that the spike has the fruit much less dense and sometimes rather gappy.  The spikes remain underwater and the pollen is carried from flower to flower by water.  In the main pondweed group the spikes are emergent and wind-pollinated.

 

Potamogeton pectinatus

Photo Carl Farmer
6 Aug 2003 Dunvegan, Skye

 

Potamogeton pectinatus

Photo Carl Farmer
6 Aug 2003 Dunvegan, Skye

  Potamogeton pectinatus

Photo Carl Farmer
6 Aug 2003 Dunvegan, Skye
Fruiting spike 12 mm long

 

Potamogeton pectinatus

Photo Carl Farmer
6 Aug 2003 Dunvegan, Skye
Ruler divisions are millimetres

  Potamogeton pectinatus

Photo Carl Farmer
6 Aug 2003 Dunvegan, Skye

Fruits, with beak at top, attachment to stem at
bottom.  The fruit is very asymmetrical, which
distinguishes it from that of Slender-leaved Pondweed

 

 


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