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Botaniska Notiser 1946. Häfte 2. Lund
Pseudanabaena biceps, a New Sapropelic Species
from Bottom Mud.
Bv Tyge W. Böcher.
Botanical Institute, University of Copenhagen.
In the small and shallow brackish water lake. Flvndersø. in the
vicinity of Rørvig (NW-Sealand) the bottom is covered by a layer of
mud which smells rather strongly of sulphuretted hydrogen. The
Cyano-phyta-flora in the upper part of this bottom mud has been studied in
some detail. It contains some species of Microcystis and Chroococcus,
a large number of species belonging to the genus Oscillatoria, and one
species which may be referred to Pseudanabaena. This genus was
de-scribed by Lauterborn (1915. p. 437) in bis work ön sapropelic
organisms from bottom mud (»Faulschlam»).
According to Lauterborn Pseudanabaena is characterized by the
clearly separated cells, the distinct chromoplasma and the large
mobi-lity of the thrichomes. T wo species. viz. P. constricta and P. catenata,
have been described. The cells of the former are constricted in their
central part. Both are only found in bottom mud as is the case with
a third species. P. tenuis, found låter by Koppe (1924).
In his t wo works (1925, 1932) ön the Cyanophyta Geitler. mainly
ön the basis of a single observation made bv Koppe (I.e.). has referred
P. constricta to the genus Anabaena. and he evidently doubts the
justification of setting up the genus Pseudanabaena, calling it a
»Verlegenheitsgattung». Koppe mentions and pictures only two rounded cells,
which were found in one case in P. constricta. From his description it
is not clear whether these two rounded cells had the wall-structure and
colour which characterize heterocysts. Thus. their nature seems rather
obscure, and further observations are needed before a definitive
refer-ring af P. constricta to Anabaena.
In a footnote Geitler (1932, p. 874) mentions the investigations of
Cannabaeus (1929). He writes that »Cannabaeus konnte auch bei
anderen Anabaena-Ar\en durch anaerobe Kultur »constricta»-Formen, d.h.
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