The Botany of Iceland - 01.12.1928, Side 28

352
JOHS. BOYE PETERSEN
Several investigators (Esmarch (1911 and 1914), Boye Petersen
(1915), Bristol (1919 and 1920), Moore and Karrer (1919), Moore
and Carter (1926)) have studied the terrestrial algæ by means of
cultures. In cultures there will as a rule develop species quite diffe-
rent from those found in the samples on simple microscopical
observation. Hence, if the two methods of investigation are com-
bined, as complete an algal ílora as possible will be obtained.
However, as a basis for even the roughest estimate of the frequency
of the individual species, the methods of culture hitherto employed
are quite useless. If, therefore, a description of the individual algal
associations and the proportion of their components in Nature is
aimed at, direct investigation of collected samples is for the present
to be pi'eferred. In the present work I have exclusively employed
this rnethod. There is however, no doubt that by means of cul-
tures more terrestrial species may be demonstrated than tliose here
mentioned. At my instigation Mr. Molholm-Hansen has collected
a series of samples of eartli from Iceland in sterile glasses, and
these I have used as a starting-point for cultures in which numerous
species of algæ have appeared. I hope to be able to publish the
results of this investigation later on.
1. Soil.
The loose soil of Iceland may consist of a series of different
components of widely varying geological origin. The cominonest
are perhaps glacial formations, but also alluvial formations such as
river gravel, sand, and clay are common, while drift-sand often
occurs, especially in the interior. Mixed with these soils are nearly
always found smaller or greater amounts of volcanic dust, and in
the neiglibourhood of the volcanoes the soil consists almost exclu-
sively of volcanic ashes and dust. Covering the mineral soil there
is as a rule a Iayer of hurnus which is often turfy. (See Thorodd-
sen 1914, p. 251). Little is known of the chemical composition of
the soil. As a rule however, it seems to contain little calcium car-
bonate, but much phosphoric acid and iron (Thoroddsen 1914,
p. 252). According to Uspenski (1927) the presence of this sub-
stance in greater or smaller amounts is of signal importance to the
lower plants. This miglit perhaps be studied to advantage in Ice-
land. Thoroddsen states (1. c. p. 253) that the soil is as a rule
covered with acid boggy humus. Mr. Molholm-Hansen lias
made a series of determinations of the pH value of soil and springs