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ZYGNEMA 41
spores in one of the gametangia; receptive gametangia slightly enlarged
on the conjugating side; zygospores globose to ovoid, slightly com-
pressed, /i. 30-36 X 30-46^1; median spore wall blue, scrobiculate; pits
1.5-2 ju. in diameter, 2-4 /^ apart; aplanospores similar, 30-34 /a x 30-80 /a,
filling the cells.
United States: Illinois.
SPECIES REPRODUCING BY APLANOSPORES
80. Zygnema frigidum Taft 1934. Trans. Amer. Micros. Soc. 53,
p. 214, PI. 17, Fig. II.
Vegetative cells 21-23JU, x 29-83/A; conjugation unknown; reproduc-
tion by aplanospores, cylindric to tumid-cylindric with rounded ends,
22-24^1 X 24-44 /x; niedian spore wall blue, scrobiculate; pits 1.5-2;". in
diameter, 3-4 /t apart. (PL i, Fig. 6.)
United States: Oklahoma; Texas.
81. Zygnema spontaneum Nordstedt 1878. De Algis et Characeis
Sandwicensibus, p. 17, PI. i, Figs. 23-24.
Vegetative cells 16-22/i x 28-90 /a; reproduction by aplanospores
only; aplanospores ovoid to cylindric-ovoid, 18-22^1 x 22-32 /x; median
spore wall brown, scrobiculate; pits about 2iu in diameter, 3-5 /^ apart.
(PI. VII, Figs. 5-7.)
Hawaii; South Africa (E. Stephens Coll.); Java (Czurda); China (Jao).
At all the above stations this species produced only aplanospores. The
illustrations, published by G. S. West (1909) under this name, showing
scalariform conjugations are better illustrations of Z. subtile than of this
species. Nordstedt's original collection from Hawaii had cell diameters of
i6-i8ju; the South African material, 18-20 /x; and the Szechwan specimens,
19-22 ;u.
82. Zygnema cylindricum Transeau 1915. Ohio Jour. Sci. 16,
p. 22.
Vegetative cells 28-33 ft x 28-66 /x; conjugation unknown; reproduction
by akinetes and aplanospores; aplanospores cylindric to tumidcylindric,
filling the cell, 30-33 /x x 24-54 /x; median spore wall brown,
scrobiculate; pits about 3^ in diameter; suture irregular. (PI. VII,
Fig. 9-)
United States: Illinois; Indiana; Kentucky; Ohio. Common and generally
distributed in April and May.
South America, south Chile.
83. Zygnema sterile Transeau 1934. Trans. Amer. Micros. Soc.
53, p. 212.
Vegetative cells 44-54 /^ x 22-69^1 with heavy cell walls, often with