The Botany of Iceland - 01.12.1912, Blaðsíða 165

MARINE ALGAL VEGETAI’ION
151
algæ occur. The following species are common or, at least, occur
very socially: —
Chantransia Alariæ.
Rhodochorton membranaceum.
R. penicilliformis.
Ascocyclus islandicus.
Ectocarpus tomentosoides.
Litosiphon filiformis.
Myrionema Corunnæ.
Phæostroma pustulosum.
Pylaiella litoralis.
Streblonema Stilophoræ.
Acrosiphonia incurva.
Ulothrix flacca.
All the remaining Edocarpns-spccies which are found on the
stipes occur in addition. Of the species mentioned there are three
in particular which grow very socially: Cliantransia Alariœ covers
tlie entire frond of Alaria esculenla from tip to base; Ectocarpus
tomentosoides also grows very socially on the fronds of Laminaria
hyperborea and L. digitata which it frequently, entirely or nearly,
covers during spring-time, at which time, also, Litosiphon filiformis
often covers large portions of the lamina of L. saccliarina.
Mgrionema Laminariœ and Streblonema æcidioides, in addition,
grow as endophytes in the Laminaria fronds.
Thus, at ieast 62 species of marine algæ, or about 59 % of the
algal species (113) which grow below the limit of low-tide, occur
on or in Laminariaceœ.
On other coasts, those of the Færöes, for example (Börgesen,
11 and 12), and those of Norway (Boye, 10) a similar epiphytic
vegetation occurs in the Lummana-association. On the coasts of
Greenland (Rosenvinge, 63) the epiphytic vegetation is much
scarcer in the Laminaria-he\t, which is possibly due, in part, to
the absence of Laminaria hyperborea from that country.
15. The Desmarestia-association.
Desmarestia acuteata is very common and grows both scattered
and socially; vertically it is widelv distributed, as it has been found
at depths of from 4—60 metres (in E. Iceland). It seems to grow
most luxuriantly at a depth of about 6—30 metres, and then is
frequently found in associations of lesser extent. Only rarely is
this association found dominant on the bottom, and even then only
in small patches. Most frequently it occurs intermingled with other
associations; thus, when dredging on a Laminaria bottom, il
very frequently happens that Desmarestia aculeata is brought up,
and as frequentlj7 as not it is intermingled with the associations
which extend deeper down. It often grows among the Laminariœ,