The Botany of Iceland - 01.12.1928, Page 23

COMMUNITIES OF AERIAL ALGÆ.
I. ALGAL VEGETATION ON PROMINENT OBJECTS.
1. On Woodwork and the Bark of Living Trees.
^T^he cliraate of Iceland is very damp, that is to say, rain is fre-
quent all the year round, and altogether rainy days are very
numerous. Thus it is stated that at Stykkisholm there are on an
average 205 rainy days annualljr. On the other hand the absolute
amount of the rainfall is not very great, and naturally there are
considerable local variations.
Consequently, when I went to Iceland in 1914 to study the
aerial algæ, I liad expected that all woodwork, fence-poles, the
wooden gables of houses, and the trunks of the birchtrees would
be green with a coating of algæ. My expectations on this point
were, however, entirely disappointed. It turned out that all pro-
minent woodwork as well as the trunks of the very sparsely occur-
ring trees were practically entirely devoid of any such algal vegeta-
tion. The woodwork forming the gables of the turf houses was
quite naked, almost white, bleached with the sun, wind, and rain.
Only right at the bottom did I occasionally find a scanty algal
growth, e. g. at Hrafnkelstaðir (79) (E. Icel.), where I found a layer
of Myrmecia pyriformis, and at the bottom of a barn-door at Möðru-
vellir (Kjós) (292), where I found Desmococcus vulgaris, Pleurococcus
vulgaris, and Trochiscia hirta.
On two palings in Reykjavík I found layers of green algæ (276,
286) consisting in one case of Apatococcus lobatus, Coccomyxa dispar,
Desmococcus vnlgaris, in the other of Apatoccus tobatus, Chlorella
ellipsoidea, Pleurococcus vutgaris.
Fence-poles and telegraph-poles were as a rule quite devoid of
vegetation. However, on a fence-pole at Möðruvellir (Kjós) (287) I
found Botrydiopsis arhiza, Prasiota sp., Stichococcus bacitlaris, while
Chlorella rugosa and Stichococcus bacillaris grew on a telegraph pole
outside Borgarnes (349).