The Botany of Iceland - 01.12.1932, Blaðsíða 10

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POUL LARSEN
new species. This, for instance, is the case with Naucoria myosotis,
the older sporophores of which are provided with a distinct ring, and
the younger pilei of which have the gills covered with a dense filmy
veil. The same applies to several Cortinarii. The well developed
veil is also a striking feature in many species of the genera Inocybe,
Hebeloma, and Galera, though in the latter genus only in species of
the group Bryogenae Fr.
The cool and moist climate has also considerable influence on
the distribution, density, and time of fructification of the Micro-
mycetes, both directly and more indirectly, by aífecting the host
plants. The period of drought so common in Central Europe in
June and July, which arrests fructification in most of the sapro-
phytes among these fungi, is unknown in Iceland. Discomycetes and
Pyrenomycetes fructify all the summer both in the lowlands and
in the highland tracts as far as the vegetation extends. — The
withered leaves and stems of most herbaceous plants survive Ihrough
the winter and provide a fertile soil for these fungi. In Central
Europe a great many herbaceous plants appear so early that they
wither already during the drought in the summer and become a
prey to the rich bacterial life of the moist autumn, disappearing
without leaving any trace at the beginning of tlie winter. Not so
in Iceland where these plants appear late. Their decay occurs at
such an advanced stage of the summer that the cold and snow-
covering prevent the breaking down activities of the bacteria and
the fungi, and when the snow-covering melts in the succeeding
early summer, large quantities of withered leaves and steins are left,
on which numerous fungi thrive. These, in conjunction with the
bacteria, complete the work of decay. That the Micromycetes com-
peting with the bacteria in the dissimilation of the vegetable sub-
stances are stronger in this climate than in Central Europe appears
from the greater abundance with which these fungi occur on the
decaying parts of plants. While the collector in Central Europe must
examine withered leaves and stems very carefully in the field if he
wants to bring home any spoil at all, a quite inexperienced collector
may gather a rich harvest of Micromycetes in Iceland by merely
collecting at random any dead parts of plants at any time of the
summer.
The luxuriant development of this microflora may be in part
due to the fact that the phanerogams have a looser structure and
feebler strengthening tissue tlian the same species of plants in more