The Botany of Iceland - 01.12.1928, Side 95

THE AERIAL ALGÆ OF ICELAND 419
Nitzschia vitrea Norman v. salinarum Grun. Cl. und Grun. Arct.
Diat. p. 94. Van Heurck Syn. Pl. 67, íig. 12.
Vestmannaeyjar L. 401, L. 403, L. 410.
According to the literature this species is a brackish water and
marine species. 0strup had previouslv found it in a sample from
fresh water from the Vestmannaeyjar. Since it was found in numerous
specimens with cell contents in the samples mentioned, it has been
establislied with certaintj' that it can grow on land. Even though it
was found at rather a great height above the level of the sea (20 m) it
is quite possible that it may be reached by the salt water spray in
stormy weather, and this may possibly be a life condition for it.
CHLOROPHYCEÆ.
There is a strong tendency at present to try to revive old forgotten
names of species and genera within the green algæ in order to improve
tlie nomenclature as lias been successfully done to a great extent within
the phanerogams. Among the unicellular algæ, however, the matter is
much more difficult, partly because the descriptions and flgures in the
earlier literature are most imperfect, and partly because original spe-
cimens are often lacking. And even if such are found in the form of
exsiccata, it is often very difíicult, even upon most careful examination,
to arrive at decisive results by the aid of them, as has been correctly
pointed out e. g. by Brand (1924, p. 324). In my opinion, therefore,
one cannot be critical enough with regard to that kind of invesligations,
and I shall have occasion to express my doubts as regards several of
them under the individual species.
The present investigation has been based almost exclusively on
material collected in the dried condition by myself during the summer
of 1914. While saniples thus collected remain almost unchanged in the
case of true aérial algæ for weeks, months, nay often longer periods,
because the algæ still remain alive, it is quite otherwise after the lapse
of several years. Then the cells will gradually die, the cell contents
shrink somewhat, and even after prolonged soaking in water it is difflcult
to recognise the exact structure of the cell contents, especially chroma-
tophores, pyrenoids and cell nuclei. Special methods must be resorted
to in order to soak the cells and attempt by chemical means to make
the desired structures appear. For soaking Lagerheim’s lactic acid
method (1888) has yielded excellent results especially with succeeding
rinsing and treatment with potassium tri-iodide. For the demonstration
of pyrenoids with starch (cf. Brand 1925) I have very successfully
employed chlor-zinc-iodine which e. g. in Prasiola will bring out the
pyrenoid surrounded by blue grains of starch very handsomely.
As was to be expected, the method indicated by Geitler in which
nitrate of silver was employed to make the chromatophores appear dis-
tinctly, proved unavailable in tlie case of dried material.