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CHAPTER NINE
THE GENUS MOUGEOTIA C. A. AGARDH 1824
Plants belonging to this genus were figured and described as
early as 1803 by Vaucher in his Histoire des Conferees. Agardh,
however, was the first to classify these plants in a way that clearly
distinguished them from other "conjugates." During succeeding
years of the nineteenth century there was much confusion about
the nature of the group of cells now called the spore, sporangium,
and the gametangia. Some authors interpreted the group of cells
as the spore; others thought the gametangia and conjugating tube
constituted a "carpogonium." When the gametangia became
divided by the sporangium walls, the ends of the gametangia were
looked upon as "sterile cells," since they are not empty but contain
"cytoplasmic residues." Hence, many descriptions until those of
very recent years contain the statement that the spore, or "fertile
cell," is adjoined by two, three, or four "cells" instead of two,
three, or four dead ends of the gametangia. Apparently, because
of the "residues," many authors could not see the complete homology
between these reproductive structures and those of Zygnema.
Because of the emphasis placed on the reproductive structures,
the position of the "fertile cell" relative to the remnants of the
gametangia became the basis of several genera which have been
discarded by most authors. These generic names are only of
historic interest and are listed at the end of the section. Plants of
this genus are generally simple filaments of cylindric cells. Rarely
one celled or two celled branches occur, particularly near the bases
of filaments where the latter are anchored by coiling around a
support or are attached to some substrate by rhizoids.
The vegetative cells are comparatively long, five to twenty
diameters, with plane end walls that are thinnest at the center.
Hence when the cells of a filament separate, the free ends are
usually somewhat conical. Each cell has one or two axial, flat
chromatophores extending the full length of young cells but
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