The Botany of Iceland - 01.12.1928, Side 56

380
JOHS. BOYE PETERSEN
have had it in a living state. I found several specimens of it in the
above-mentioned locality, some of them with cell contents. Sometimes it
occurred in small groups consisting of 3—4 individuals.
The locality was rather peculiar. At a height of 540 m
on the heath between Isafjord and Flateyri, on the stony
flat surrounding the beacon at the highest point, were
found tufts of Prasiola crispa with other green algæ and
some Diatoms intermixed. The place no doubt often
serves as a halting-place for travellers on foot or on
mœaCSchunOcÍ horseback, and one can hardly lielp thinking that such
(X 1200). a tuft of algæ may have been brought up there acci-
dentally by people or horses, but the algæ seemed to
be in a flourishing condition.
One specimen measured in 1.11,5 p, br. 6,2 /u, str. 16. The same species
was found in a sample of soil from Björk taken in 1925 by Molholm-
Hansen. Here I observed that the apical area of the hypotheca was
now broad, now narrow. In the specimens in this sample the striæ
seemed to be somewhat finer, viz. 18 in 10 /t in both valves.
Achnaníhidinm Heib.
Achnanthes coarctata (Bréb.) Grun. Cleve Syn. II, p. 192. V. Heurck,
Syn. Pl. 26, figs. 17, 18.
E. Icel. L. 70 — N. Icel. 253 — S. Icel. 302 — Vestmannaeyjar L. 399,
L. 400, L. 401, L. 403, L. 408, 409.
The species seems to be most widely distributed in the northern
hemisphere and especially in arctic regions. Pfitzer mentions it as far
back as 1882 (p. 405) as a terrestrial species. In Denmark it frequently
occurs as an aérial alga (Boye P. 1915, p. 293). In Switzerland Meister
considers it rare (1912, p. 99), while v. Schönfeldt’s statements from
Germany (Pascher, Siisswasserflora, H. 10, p. 58) would seem to indi-
cate that it occurs especially in »formations passagéres« (sensu Comére).
As regards the arctic countries Lagerstedt states (1873, p. 49) that it
is fairly common in Spitzbergen and Jan Mayen, and occurs »on the
ground and among mosses*.
In Iceland 0strup found it in 39 samples, while I have it from 9.
It may then perhaps be warrantable to assume that it thrives about
equally well in water and in certain aérial localities, though in Den-
mark it seems to be predominantly a terrestrial species. On the rocks
of the Vestmannaeyjar it was a character species, occurring in nearly
all the samples collected partly from caves in a rocky wall at an alti-
tude of about 20 m above sea Ievel, partly on rocks below bird cliffs.
In the caves in question it was found inter alia together with several
brackish water species.
Achnanthes lanceolata (Bréb.) Grun. Cl. Syn. II, p. 191. V. Heurck
Syn. Pl. 27, figs. 8-11.
E. Icel. 128 - N.Icel. 162, 179, L. 215, L. 217 - S. Icel. 364, 372,
395 — Vestmannaeyjar L. 403, 408.
Fig. 5.