Fróðskaparrit - 01.01.1996, Side 79

SPECIES ON THE ALGAL GENUS VAUCHERIA ON THE FAROES
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branch often increases markedly and even-
ly upwards, and the oogonia become rela-
tively short-stalked, crowding subterminal-
ly around the terminal antheridium like in
the alga named V. trigemina by Kiitzing
(1856). Where there are only two oogonia
their orientation varies considerably. They
may be almost upright, or they may bend
horizontally as is also often seen in V. gemi-
nata s. str., or they may even be pendent
much like in V. prona. One and the same
filament may carry an almost straight fruit-
ing branch with two or three oogonia to-
gether with a bent fruiting branch with two
pendent oogonia. As a result, identification
of scanty prona-Uke filaments in samples
not studied in culture must be regarded as
uncertain, and such filaments have been left
unmentioned here. Good material of the
trigemina-like alga has been found in the
samples 3,5,6,8,9 and 16, five of them be-
ing studied in unialgal culture.
V. međusa T. A. Chr. 1952 has been found
in the samples 13, 14 and 15, all from the
same salt marsh, collected in places only
little influenced by sea water.
V. prona T. A. Chr. 1970 forms abundant
fruiting branches as well as asexual spores
in sample 10. All the oogonia seen are
aborted, however, perhaps suggesting that
the alga is close to its geographical boun-
dary. Many of the asexual spores are small-
er than typical and less regular in shape,
again suggesting environmental stress, but
they germinate all right irrespective of such
irregularities.
V. uncinata Kiitz. 1856 has been found in
the samples 5 and 7. The sample listed by
Børgesen (1901) as V. hamata, collected at
Nes on Eysturoy, UTM about 29 E 619 N
6885, represents the same species, which
was poorly known until the taxonomy was
cleared up by Blum (1953. V. uncinata
shows considerable variation as to oospore
dimensions. A histogram for Børgesen’s
material has been published previously
(Christensen, 1986). The two samples from
1994 differ little from it, 25 spores from
sample 7 showing an average width of 138
pm and an avarage length of 126 ^m.
Three parasites have been encountered in
the Vaucheria material:
A single gall of the kind produced by the
rotatorian Proales werneckii (Ehrb. 1834)
was observed in a young crude culture
based on sample 3. The culture was left un-
touched in order that filaments might later
be found with galls and sexual organs to-
gether, permitting a specific determination
of the algal host, but later search for galls
was unsuccessful.
The plasmodiophoralean Woronina glom-
erata (Cornu 1872) Fischer 1892 was pre-
sent in a crude culture of the V. geminata
ally based on sample 16.
The chytrid Zygorhizidium vaucheriae
Rieth 1967 has been found on V. canalicu-
laris in sample 10.