The Botany of Iceland - 01.12.1928, Qupperneq 75

THE AÉRIAL ALGÆ OF ICELAND
399
Navicula cryptocephala Kiitz. var. angusta Boye P. n. var.
Valva lineari-lanceolata, subrostrata, apicibus rotundatis;
long. 18 ju, lat. 3,7 /á, striis 18 in 10 /u. Fig. 21.
E. Icei. 7, 124 — N. Icel. 169, L. 217 — S. Icel. L. 386.
Differs from the other varieties of the species especially
by its narrow form and its comparatively broad apices. Only
found in places with plenty of moisture, it does not pro-
bably withstand desiccation very well.
— — var. exilis Kutz. Cl. Syn. II, p. 14. Van Heurck
Syn. Pl. VIII, íig. 2, 4.
Fig. 21.
Navicula
cryptoce-
phala Kutz.
var. artgusta
n. var.
(X 1200).
N. Icel. 169 — S. Icel. L. 386.
Ostrup found this variety in 25 samples from fresh water, and it is
probably no aérial form. Both my samples are from very damp localities.
----var. veneta Kútz. Cl.Syn.II, p. 14, Van Heurck Syn. Pl.VIII, íig. 3.
N. Icel. L. 215, L. 217, L. 218.
I have found this form in Denmark living on garden soil and mea-
dows. The 3 samples from Iceiand in which I found the species are
all from Stóra Gjá, the remarkable basalt cleft east of Mývatn, which is
always damp because a hot spring flows out into the bottom of tlie
cleft. 0strup has not mentioned this variety as occurring in Iceland.
Navicula Falaisiensis Grun. var. lanceola Grun. Cl. Syn. II, p. 21.
Van Heurck Syn. Pl. 14, fig. 6b. Van Heurck Types No. 127.
E. Icei. 125.
I have previously found N. Falaisiensis on earth in Denmark. As
it belongs on the whole to the iess frequent species, and has not been
found in Iceland before, it is possible that it is really an aérial species.
Navicula Gastrum Ehrb.var. exigua Greg. Cl. Syn. II, p. 23. Van Heurck
Syn. PLVIII, fig. 32.
N. Icel. 218.
I have previously found this variety on arable land in Denmark
(Boye Petersen 1915, p. 292). 0strup found it in 10 samples from
■Iceland, so probably it is hydrophilous.
Navicula peregrina Ehrb. var. Meniscus Schum. Cl. Syn. II, p. 18.
Van Heurck Syn. Pl. VIII, fig. 19.
Vestmannaeyjar L. 399, L. 401.
According to Cleve this is a brackish water species, but it may
evidently also occur in quite fresli water. On the Vestmannaeyjar I
found it in caves in a rocky wall at a height of abt. 20 m above the
sea. It cannot be considered quite precluded that it may be dashed
with foam and spray from the sea in stormy weather.