B
ackhaus
:
Phormidium ingrediens sp. nova
19
mentioned in the literature. Furthermore, the dif-
ferent reactions towards the staining of sheaths
with chlorine-zinc-iodine-solution are of particular
importance: P. corium reacts positively, “Phormid-
ium spec.” negatively. At last we must consider
the different autecology of both taxa: In contrast
to the wide ecological valence of P. corium, as it
can be deduced from its widespread occurrence,
“
Phormidium spec.” offers a distinct reference for
streamwaters of specific physico-chemical char-
acter as shown further down.
Phormidium inundatum K
uetzing
ex
G
omont
1892
Just as said for Phormidium corium also for P. in-
undatum several remarks indicate a greater dis-
tance to “Phormidium spec.”: Greater dimensions
of trichome widths and cell lengths, the positive
staining with chlorine-zinc-iodine solution, the
forming of membranaceous thalli and the colo-
nizing of other biotopes than low scale chalk
streams. Of additional particular importance may
be the brief attenuation of the trichome ends as it
is implied also for Phormidium corium (K
omárek
&
A
nagnostidis
2005),
but is not found for “Phor-
midium spec.”. The noted granulations at the
cross walls should not be a diacritical feature.
Looking at all their taxonomic criteria, P. corium
and P. inundatum differ insignificantly, with the
likely consequence that mix-ups and false assign-
ments of samplings should be expected frequent-
ly. For example, even in the “Süßwasserflora von
Mitteleuropa” (K
omárek
&
A
nagnostidis
2005),
the same illustration appears for both P. inundatum
and P. corium (figs 618 b and 660 d). Because of
the occurrence as cosmopolitans as well as their
similar autecological profiles, the combination of
both taxa would be obvious. An identification with
“
Phormidium spec.” should be excluded for P. in-
undatum just as it is for P. corium.
Phormidium taylori (D
rouet
&
S
trickland
)
A
nagnostidis
2001
The continuous straight line of the trichomes as
well as the isogeometric shape of the cells com-
bined with lowest diameters beginning at 4 µm
initially make P. taylori appear to belong to the
species group looking like”Phormidium spec.”.
But in the majority cell diameters span 6-7 µm,
and this aspect must be considered to be a sig-
nificant difference in comparison to 2,9-4,2 µm of
“
Phormidium spec.”. In addition, slight constric-
tions at the cross walls are apparent. Finally, the
benthic predominant occurence in still waters
and the tuft-like structure of the thallus are to be
taken into consideration. Taken together, the fac-
tors mentioned above make the identification of
P. taylori with “Phormidium spec.” very doubtful.
Phormidium rimosum (K
omárek
)
A
nagnostidis
&
K
omárek
1988
The following properties of Phormidium rimosum
show similarities with “Phormidium spec.”: The
potential chasmoendolithic habitation, the partly
parallel-orientated filaments, the straight form of
the trichomes without any attenuation, hardly vi-
sible cross-walls, and the slightly obtuse conical
terminal cells. On the other hand, the differing
features are clearly predominant: The total lower
trichome widths of only 2,6-3,2 µm, the shape of
the cells as distinctly shorter than wide, constric-
tions at the cross walls, which may be slight but
obvious. Further differences are the conspicuo-
usly thickened sheaths and the presence of this
species in wooden creeks, which are free of lime.
With respect to these characteristics, the assi-
gnment of the carbonate- boring “Phormidium
spec.” to P. rimosum should be excluded.
(2)
Species with carbonate incrustations
Phormidium incrustatum G
omont
ex
G
omont
1892
Phormidium toficola (N
ägeli
)
G
omont
ex
G
omont
1892
Phormidium umbilicatum (N
ägeli
)
G
omont
1892
The mutual morphological differentiation of these
threePhormidium-species fromone another is dif-
ficult, because they are identical in essential fea-
tures and differ only very slightly in the trichome
widths. For P. toficola and P. umbilicatum, the
width-spans of 3-4,5 µm, respectively 3-4,8 µm
are practically identical. They are embedded in
the range of 3-6,5 µm for the trichomes of P. in-
crustatum. These aspects caused K
ann
(1973)
to consider all three together as a taxonomic
unity, since E
lenkin
(1949)
and S
tarmach
(1966)
already pointed out these similarities. P
entecost
(2003),
in his examination of Phormidium in-
crustatum, did not support this point of view. The
taxonomic position of these three taxa, however,
remains undecided until now since K
omárek
&
A
nagnostidis
(2005)
did not include P. toficola
into the revision of the phormidians and refer to
P. incrustatum (p.425). For this reason, a sepa-
rate discussion of the single taxa will be related
to P. incrustatum only.
