The Botany of Iceland - 01.12.1928, Side 48

372
JOHS. BOYE PETERSEN
II. Tabellarieæ.
Tabellaria Ehrb.
Tabellaria fenestrata (Lyngb.) Kötz. V. Heurck Traité p. 35G, Pl. 11
flg. 477.
E. Icel. 25.
Only a few specimens observed. It is evidently of erratic occurrence.
Tabellaria flocculosa (Roth) Kútz. Van Heurck Traité, p. 357, Pl. 11
flg. 478.
E. Icel. 25, 129.
No doubt the occurrence is merely accidental, as in the preceding
form. The specimens have hardly lived in the localities mentioned (rocks).
Diatomella Grev.
Diatomella Balfouriana Grev. W. Smith Br. Diat. II, Tab. 61, flg. 383.
E. Icel. 8, 14, L. 24, L. 25, 40, 70, 77, 78, L. 85, L. 92, L. 99, 112,
113, L. 114, L. 124, L. 128, L. 129.
N. Icel. 133, 135, 137, 162, 169, 179, 184, 185, 241, 242, 252, 256.
W. Icel. 294, 307, 321, 336, 338.
S. Icel. L. ? 294, 295, 372, 386.
Diatomella Balfouriana is a pronounced Arctic-Alpine species, thriving
especially on irrorated rocks with mosses or algæ (see e. g. Hustedt
1924 p. 550, v.Schönfeldt 1913 p. 27). Hustedt, however, says (1. c.)
that it only grows »im Urgebirge*. In Iceland, however, primitive rock
does not occur. We must tlien suppose that most probably it only grows
on eruptive rocks and especially not on limestone rocks. In this connec-
tion it is remarkable too that the species has not been found in Den-
mark.
0strup found it in Iceland in 168 samples from fresh water. In
most of the above-mentioned samples I only found few specimens, and
it was not possible to see any cell contents. In this species, however,
the chromatophores are but little conspicuous in the dried material, so
there maj' possibly have been specimens with endochrome in not a few
more samples than the 7 in which I have seen them with certaintj».
On the other hand the frustules are ratlier strong, and thus no doubt very
durable, so that we might expect to find the empty frustules in places
where the species has not lived. It is, however, remarkable that 6 of
the 7 samples are derived from rocks, or mosses on rocks, that were
more or less damp.
It was known from early times and has again been pointed out
by N. Carter (1922 p. 56) and Hustedt (1924 p. 550) that this species
is provided with a true raphe. This circumstance vill presumably render
it well suited for an aérial life. (Cp. Boye Petersen, 1915, p, 298).
It would seem from the data that the species may occur both as
an aérial and as a hydrophilous alga.