FUNGI OF ICELAND 459 
southerly latitudes. For the leaves this has been demonstrated by 
Dr. F. Borgesen in his paper »Bidrag til Kundskaben om arktiske 
Planters Bladbygning« in Botanisk Tidsskrift, Vol. 19, Copenhagen 
1895, and by Bonnier in »Comptes rendus« 1894, t. CXXIII, p. 1427. 
— As a circumstance pointing in the same direction I may men- 
tion that a great many Cyperaceae which are quite valueless as 
fodder in Central Europe, are highly valued feeding plants in Ice- 
land both for horses and cows. Icelandic hay is »richer in nourish- 
ment« than hay in more southern latitudes — in its native land the 
Icelandic pony can work on a fodder of hay alone, which perhaps 
shows that the Icelandic plants have a feebler mechanical tissue 
and therefore are more easily digested and give a greater surplus of 
energy to the animals.! 
That the epidermis of these plants is thinner and the cuticle 
weaker appears plainly enough in the preparation of the perithecia 
of Pyrenomycetes or pycnidia of Sphaeroidaceae imbedded in their 
leaves and stems. It is much easier than the same work with leaves 
and stems of similar plants in Central Europe. The looser structure 
evidently makes it easier for the hyphae of the fungi to penetrate 
into the body of the plants. Also the predominant isolateral struc- 
ture of the leaf (see Borgesen’s above-mentioned paper) renders 
invasion easier, as there are stomata on either side of the leaf. 
Immigration of the Fungi into Iceland. 
While the answers to the questions dealt with above relating 
to the fungi of Iceland were based on facts or on conclusions 
drawn from facts, the case is different when we attempt to solve the 
problem treated in the present section. 
In the first place our knowledge of the geographical distribu- 
tion of the species of fungi is rather uncertain. In the second place 
we do not know the full extent of the means the fungi have of 
! Compare the quotation from P. Feilberg at p. 253, vol. I of this work, and 
the references to the literature. From these it would seem to appear that in Feil- 
berg’s opinion Icelandic ponies and cows have in the course of many generations 
adapted themselves to the Icelandic Cyperaceae and »coarser« grasses, and that it 
may be partly owing to this circumstance that they derive so much nourishment 
from these plants. But this argument does not cover the facts, for, when in Den- 
mark, Icelandic ponies are unable to work on hay alone, but must have oats added 
to their fodder. 
