The Botany of Iceland - 01.12.1928, Side 112

436
JOHS. BOYE PETERSEN
On Heimaey I also found it on woodwork so near the shore that
it could be dashed by the salt water spray at any rate in stormy weather,
but likewise on a big stone bj' the shore.
Trentepohliaceæ.
Trentepohlia aurea (L.) Mart. Hariot 1890, p. 192.
Helgi Jónsson mentions (1900, p. 93) that the species »is of com-
mon occurrence in the faintly lighted grottos of the lava flelds: here it
grew everywhere in the small lava holes, and often it was the only
plant of the grottos*. This is said about Snæfellsnes, but it probably
applies to other parts of Iceland too. Unfortunately there is no collected
material of the species, and as I have not found it myself, I have
nothing to add.
Trentepohlia sp.
An imperfectly developed Trentepohlia was found on Heimaey on
a large stone outside a cave at a height of abt. 20 m. It bore most
resemblance to T. umbrina, but as no gametangia were present, it could
not be determined with certainty (sample 400).
Siphonocladiales.
Cladophoraceæ.
Rhizoclonium lapponicum Brand. Brand 1913, p. 180:
Vestmannaeyjar 399, 410.
In a rocky cave on Heimaey, aht. 20 m above the level of the sea
on highly calciferous sand with trickling water occurred green cushions
consisting of Vaucheria sphœrospora and a Rhizoclonium which seemed
to me to correspond quite well with R. lapponicum Brand. It formed
rippling masses of filaments, yellowish-green in the dried condition. The
filaments were 36—39 p, thick, with cells l1/* times as long as they were
broad. The »bostrychoid* branching described by Brand was common,
but unicellular rhizoids were also present, while some of the pluricellular
short branches formed rhizoid-like terminations. A similar form was
found on rocks below bird-clitfs on the same island.
Siphonales.
Vaucheriaceæ.
Vaucheria borealis Hirn. Hirn 1900, p. 87.
E. Icel. 86, 93.
As Heering points out (1907, p. 150), Vaucheria borealis bears a
great resemhlance to V. pachyderma Walz. There seems, however, to be
a real difference between the two species in the appearance of the an-
theridium, which is tubular in the former, »beutelförmig« in the latter.
However, V. pachyderma var. islandica Borgesen (1898, p. 137) has the