458 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 Cortinarit. The well developed 
veil is also a striking feature in many species of the genera Jnocybe, 
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 affecting 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 through 
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 the 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 stems 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 than the same species of plants in more 
