The Botany of Iceland - 01.12.1928, Side 5

THE AERIAL ALGÆ OF ICELAND
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observed by O. Muller (1899, p. 282) in various genera and species
in highly saline pools and springs in Egypt, and Krasske
(1927, p. 270) in liighly saline springs in Germany. In both cases
the salinity varied greatly, and Krasske thinks that craticular for-
mation occurs when the protoplast contracts away from the wall
in consequence of a strong concentration of the salt solution, hence
in a plasmolysed state. Geitler, too, observed craticular formation
in Anomoeoneis sphœrospora (1927), but gives tack of nourishment
as the cause of the malformation. From the data there can hardly
be any doubt that tlie craticular forms are teratologic formations
produced by tlie cells, in a plasmolysed state, forming new valves
in the same way as the plasmolysed cell of a phanerogam can form
a new cell wall round the plasmolysed protoplast. In the aerial
Diatoms craticular forms are uncommon. In Iceland I have only
once observed such forms in Hantzschia amphioxys. Tlie craticular
forms cannot therefore be regarded as a kind of resting spores, they
must more probably be looked upon as teratologic formations arising
under unfavourable conditions.
As aérial algæ I will then define all algæ that do not grow in
water, or which at any rate in periods are able to grow without
being immersed in water, even if they pass into a resting stage
during protracted periods of desiccation.