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CHAPTER SEVEN
THE GENUS MOUGEOTIOPSIS PALLA 1894
These algae have simple filaments, with vegetative cells one-
half to four diameters long; each with a single quadrate, flat, or
dished platelike axile chromatophore with a thickened and minutely
granulate margin. The margin is sometimes inroUed, and
pyrenoids are absent. Oil globules occur on the surface, and both
starch granules and oil drops within the chromatophores. Reproduction
is by short to long ovoid zygospores irregularly formed
in the tube (isogamous) and extending into one or both gametangia,
but not cut off from the gametangia by a wall. Only one
species is known, from Europe and America.
This genus has had an interesting history beginning with the
description and figures published by Palla (1894). In 1898 W. &
G. S. West claimed to have found the same alga with pyrenoids
and placed it in Debarya. In 1899 Brand described a new genus
from southern Bavaria which he called Mesogerrott. His descrip-
tion emphasized the dished or partly cup-shaped forms of the
chromatophore and the absence of pyrenoids. His figure exaggerates
the curled edges of the chromatophores, as shown by an
examination of Brand's own specimens from Munich, which are
in my possession. Brand thought that his plant belonged among
the Ulotrichaceae, but Wille (1911) placed it provisionally among
the Zygnemataceae. Skuja reported the occurrence of Mesogerron
in Latvia in 1928, and in 1929 showed that "Mesogerron" is
merely the vegetative form of Mougeotiopsis. Although Czurda
(1932) insisted that the only important structure upon which
genera of the Zygnemataceae may be based is the chromatophore,
he includes this genus among the species of Mougeotia in spite of
the absence of pyrenoids, the presence of oil droplets, and the
unique thick-edged chromatophore entirely unlike that of any of
the known species of Mougeotia. It might be added further that
the zygospores, with their relatively thick and highly refractive
median walls with deep sharp-edged pits, are equally unique
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