18
carolinea, 68
(2010)
With reference to the cell dimensions, the cell
morphology and the shape of apical cells, “Phor-
midium spec.” showed similarities with Phormid-
ium corium, P. inundatum, P. taylori, P. rimosum,
P. incrustatum, P. umbilicatum, P. toficola, but also
Leptolyngbya vandenberghenii. Common to all
are trichome diameters in the range of 3-5 (7) µm,
more or less isodiametric cells and rounded or
obtuse conical apical cells. As for “Phormidium
spec.”, a conspicuous bright blue-green colour
of the thallus is ascribed to most of them. For
the present purpose they are separated into two
groups: (1) species which do not deposit calcium
carbonate, (2) species encrusting calcium car-
bonate. Phormidium kuetzingianum (K
irchner
)
A
nagnostidis
et K
omárek
1988
and Phormidium
papyraceum G
omont
ex G
omont
1892
are not
taken into consideration here (despite similar
trichome diameters), because they are subaero
phytes and settle entirely different biotopes. A
brief overall view is given also in Table 1.
(1)
Species that do not induce precipitation of
calcium carbonate
Phormidium corium G
omont
1892
Comparing “Phormidium spec.” and P. corium a
far reaching similarity in the shape of apical cells
becomes evident. They are both gently bulged
to obtusely conically rounded. Additionally the
trichome diameters seem to differ insignificantly.
These aspects make it necessary to take both
formes into a more detailed examination.
With regard to the cell dimensions frequency
histograms and statistics for the cell width and
cell length were established for both following the
procedure of P
entecost
(2003).
Fig. 15 shows
the mean of cell width in “Phormidium spec.” to
be 3,2 µm, and the cell length 3,4 µm. In fig.16
the same measurements for Phormidium corium
are 2,8 µm (width) and 4,2 µm (length). To avoid
a random choice of data, samples of three dif-
ferent locations were used each time. The dif-
ferent results of the cell dimensions may be the
initial stage in distinguishing both taxa. The gap
between them becomes greater if relating data
given in the literature are taken in considera-
tion. Very variable dimensions of trichome widths
of Phormidium corium are listed, and only the
smaller ones are compatible with those of “Phor-
midium spec.”. K
ann
(1978),
with regard to her
extensive material, indicates trichome diameters
in the majority of > 4,5 µm.
Even more the differences in the consistency of
the thallus are striking. P. corium usually forms
long, variously curved and densely entangled
filaments (figs 17, 18) and a membranaceous
or leather-like thallus. It is not plausible that pre-
cisely the cosmopolitan and probably ubiquistic
P. corium should develop a totally different lifestyle
as an endolith in the ecologically inconspicous
Black Forest streams, in contrast to its usual and
typical behaviour as surface-living form. K
ann
(1978,
p. 441) questioned whether P. corium could
possibly be carbonate boring, but she simultane-
ously emphasized the resemblance and possible
identification of her P. corium-specimens with the
endolithic Lyngbya spec. mentioned by B
ackhaus
(1968
b
)
as present in the Black Forest streams.
The question about the boring ability of P. corium
therefore should be taken up with some scepti-
cism and answered in the negative. The negative
assessment is strengthened considering the fact
that in spite of many discoveries of this taxon, no
other observations dealing with this aspect are
Figs 15, 16. Frequency histograms and statistics for the
cell width (a) and cell length (b) of “Phormidium spec.”
(
fig. 15) and Phormidium corium (fig. 16), established
from samples of three different locations, n = 200 each
time.
