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ZYGNEMA 33
the gametangia, 42-46 ,«, in diameter; median spore wall yellow-brown,
scrobiculate; pits 3/"- in diameter. (PI. V, Fig. i.)
United States: Oklahoma, Bartlesville, April 25, 1932.
This species is remarkable for the large size of the zygospores as com-
pared with the size of the vegetative cells.
46. Zygnema luteosporum Czurda 1932. Siisswasserflora Mitteleuropa.
9, p. 122, Fig. 225.
Vegetative cells 22-24/^1 x 45-80 /x; conjugation scalariform; zygospores
in one of the gametangia; receptive gametangia cylindric or
slightly enlarged; zygospores ovoid, 26^ x 38 /a; median spore wall
yellow, thick, scrobiculate, with pits widely spaced. (PI. V, Fig. 2.)
Bohemia.
47. Zygnema flavum Taft 1946. Trans. Amer. Micros. Soc. 65,
p. 24.
Vegetative cells 22-27 /a x 48-68 a^; conjugation scalariform; zygo-
spores formed in one of the gametangia; receptive gametangia cyhndric
or slightly enlarged; zygospores cylindric-ovoid to ovoid, 24-29 m x
35-51 fi; outer spore wall thin and smooth; median spore wall of 2
layers, the outer thick and smooth, the inner irregularly verrucose; both
layers light yellow; innermost spore wall thin, smooth. (PI. V, Fig. 3.)
United States: Texas, Eden, April 13, 1938. In this collection some of
the vegetative cells contained 4 chromatophores.
48. Zygnema calosporum Jao 1935. Sinensia. 6, p. 568, Pi. i.
Fig. 7.
Vegetative cells 23-26 ju x 16-48 /x; conjugation scalariform; recep-
tive gametangia shortened and greatly enlarged; zygospores globose to
subglobose, 29-35 m ^ 32-35 m; median spore wall densely scrobiculate;
pits 1.5-2.5 M^ in diameter, 1-1.5/'. apart, yellowish-brown at maturity.
(PI. V, Fig. 4.)
China, Szechwan.
Differs from Z. substellinum Taft in greater diameter of the vegetative
cells and smaller spores; from Z. vaucherii in shorter vegetative and repro-
ductive cells, and in denser scrobiculations of the median spore wall.
49. Zygnema vaucherii Agardh 1824. Systema Algarum, p. 77.
Vegetative cells 24-28 a"- x 50-180^1; conjugation scalariform; zygo-
spores in one of the gametangia; receptive gametangia gradually or
abruptly inflated toward the middle; zygospores ovoid, 24-36 ju. x 26-45 /x;
median spore wall brown, scrobiculate; pits 2-3 /x in diameter. (PI. V,
Fig- 5-)