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ZYGNEMOPSIS 53
22-25 jLi X 25-30 /"-; outer spore wall hyaline; median wall thick, chocolate
brown, smooth; aplanospores more abundant than zygospores,
asymmetrically ovoid to globose, sometimes with the 2 ends slightly
produced, 18-20/J. x 18-31 /x. (PI. VIII, Figs. lo-ii.)
United States: Michigan, Douglas Lake region (Taft Coll.).
India, Fyzabad, U.P., March, 1937.
6. Zygnemopsis desmidioides (W. & G. S. West) Transeau 1934.
Trans. Amer. Micros. Soc. 53, p. 215, Fig. 25.
Vegetative cells 8-1 i/x x 19-56 m, constricted at the ends; chroma-
tophore an axial plate with 2 pyrenoids; filaments fragment readily;
"conjugation between free cells" scalariform; zygospores formed in the
broad conjugating tubes and extending somewhat into both gametangia;
spores quadrangular with straight, concave, or slightly convex
sides and rounded angles, 14-18 m x 18-24 jw; median spore wall goldenbrown,
thick, finely punctate. (PI. VIII, Figs. 12-14.)
United States: Wisconsin.
England; Latvia.
The statement by West that conjugation takes place between free cells
is probably incorrect. Fragmentation of filaments occurs during and after
conjugation in several other species. The filaments of Z. desmidioides have
a pectic sheath. When conjugation occurs this sheath passes into solution
and, as the gametangia become distended with pectic compounds, the ends
become rounded and separate.
7. Zygnemopsis columbiana Transeau 1934. Trans. Amer. Mi-
cros. Soc. 53, p. 215, Figs. 27-29.
Vegetative cells (8-) 9.5-11.5/x x 40-ioo/x, with 2 pillow-shaped
chromatophores, each with a central pyrenoid; conjugation scalariform;
zygospores formed in the wide conjugating tubes and extending far
into each gametangium; spores quadrate-ovoid, 23-32 /a x jU-, 23-34 with
angles rounded, produced, or retuse; median spore wall with a prom-
inent suture, finely punctate, chestnut brown; aplanospores ellipsoid to
ovoid, 1 8-20 /x X 25-30^1, otherwise similar. (PI. VIII, Figs. 15-17.)
Canada, British Columbia (W. R. Taylor Coll.).
8. Zygnemopsis Americana Transeau 1934. Trans. Amer. Micros.
Soc. 53, p. 215.
Vegetative cells 9-12 /a x 27-100 /x; 2 compressed-ovoid chromato-
phores; conjugation scalariform; zygospores formed in the broad con-
jugating tubes and extending far into both gametangia; spores ovoid to
quadrate-ovoid, 20-40 /a x 30-40 /a; parthenospores 15-20 ft x 20-30 ju.,
unilaterally ellipsoid with retuse ends; median spore wall minutely