The Botany of Iceland - 01.12.1942, Blaðsíða 121
THE PTERIDOPHYTA AND SPERMATOPHYTA OF ICELAND
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37. Potamogeton filiformis Pers. Synopsis pl. I (1805) p. 152.
P. maritimum, K. & M., 1770, p. 205.—P. filiformis Nolte, Bab. 1871, p. 335.—
P. marinus L., Gronlund, Isl. Fl., 1881, p. 105.—P. filiformis Pers., Stefánsson,
Fl. ísl., ed. 1, 1901, p. 18.—Ibid., ed. 2, 1924, p. 20.—C.H.O., Fl. arct., 1902,
p. 21.—O. & Gr., 1934, p. 11.
Flora Dan. tab. 2106.
Icelandic: Þráðnykra. Danish : Traadformet Vandaks. English: Slender Pond-weed.
The records of P. maritimum, P. marinus and P. pectinatus in the older lists
may most likely all be referred to P. filiformis Pers. In Iceland this species is rather
variable. Thus two distinct varieties var. alpinus (Blytt) Almq., and var. fascicu-
latus (Wolfg.) Hagstr. occur.
Common in all parts in the lowland. Also recorded from several places in the
central highland : Fagridalur, Hvannalindir, Sauðárdalur (Steindórsson in lit. 1933).
Hveravellir (J.Gr., 1934).
Life-form : HH (Hydrophyte).
In lakes, ditches, slow-running brooks.
Flor. VI—VII; fr. mat. VII—IX.
Max. length : 75 cm ; average : 33 cm.
Geogr. area: Northern N. Am., southward to Nevada, Wyoming, Vermont.—Greenl.:
W. 60°—71°3'. E. 65°39' and 68°—74°25'.—Eur.: Fær.; E.S.I.; northern and
western Eur., southward to the Mediterranean.—Asia: Siberia, southward to Pamir,
Tibet, Kamchatka.—Africa.—Australia.
38. Potamogeton gramineus Linn., Spl. pl. ed. I (1753) p. 127.
P. heterophyllus Schreb., Babington, 1871, p. 334.—P. gramineus L., Gronlund,
Isl. Fl., 1881, p. 104.—Stefánsson, Fl. ísl., ed. 1, 1901, p. 19.—Ibid., ed. 2,
1924, p. 21.—C.H.O., Fl. arct., 1902, p. 19,—O. & Gr., 1934, p. 13.
Flora Dan. tab. 222 (a homophyllus) ; tab. 1263 (/3. heterophyllus).
Icelandic: Grasnykra. Danish: Græsbladet Vandaks. English: Grass-leaved Pond-
weed.
In Iceland this species is represented by the two common varieties or subspecies
(cp. Ascherson & Graebner, Synopsis, I, p. 322—323) : var. graminifolius Fr.,
with all leaves submerged, linear-lanceolate, usually flaccid ; the upper ones short-
stalked, at the base of the spike peduncles, without leaf-blade or only with a
very small one. Mostly in deep, or in running water. Not so frequent as the
var. heterophyllus Fr., with submerged leaves usually lanceolate, somewhat stiff,
backward-curved; upper leaves lanceolate to oval-elliptic, often with a small
point; usually long-stalked, leathery; as a rule floating on the water surface. In
shallow water. Frequent. Common in the lowland, except in N.W., where it is only
found at Bær in Rauðasandur; not recorded from the central parts.
Life-form: HH (Hydrophyte).
In lakes and ditches; in river-arms with slowly running water.
Flor. VII—VIII; fr. mat. VIII—IX.
Max. length: 110 cm ; average: about 40 cm.
Geogr. area: Am.: From Newfoundland to British Columbia, southward to Cali-
fornia, Michigan, Connecticut.—Greenl.: W. 60°—61° and 67°.—Eur.: Fær.;
E.S.I. ; northern, western and central Eur., the Balkans.—Asia: Northern Siberia
from 66° southward to Pamir, northern Mongolia; Kamchatka, Japan.