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42
ZYGNEMATACEAE
an outer pectic layer r>-i5/x in thickness; conjugation unknown; repro-
duction by akinetcs; akinetes heavy-walled, completely filling the cells,
brown at maturity, often distinctly colligate. (PI. VII, Fig. ii.)
United States: Prairie regions of Oklahoma; Texas; Wisconsin; Michigan;
Illinois; Indiana; Ohio. Not uncommon.
Greece (Skuja, 1937); Asia Minor (Skuja, 1932).
The brown color of the akinetes apparently results from chemical
changes in the protoplasts and chromatophores. I have had this alga in
cultivation during 2 successive years. It grew well, produced akinetes, which
germinated and produced new filaments. During a 5 year period near
Columbus, Ohio, it grew abundantly in a pond, but produced no spores.
84. Zygnema quadrangulatum Jao 1940. Sinensia. H, p. 294,
PI. 4, Fig. 3.
Vegetative cells 24-27 /x x 25-100 /x, with 2 stellate chromatophores;
reproduction by aplanospores only; aplanospores cyUndric-ovoid,
25-29/A X 20-28 m; median spore wall dark blue, smooth, lamellate.
(PI. VII, Fig. 14.)
China, Hunan.
85. Zygnema hypnosporum Rich 1935. Trans. Roy. Soc. S. Africa.
23, p. 125.
Vegetative cells about 33/^ in diameter, with 2 large stellate chromatophores;
reproduction by aplanospores only; aplanospores cylindric-
ovoid, 34/t X 34-70 m; median wall scrobiculate, blue. (PI. VII, Fig. 12.)
Africa, South Rhodesia, July 3, 1930 (Stephens Coll.).
86. Zygnema schwabei Krieger 1941. Zygnemales. Rabenhont'
Kryptogamenfiora. 13, p. 261.
Vegetative cells 17-20 /x x 36-71 m; reproduction by aplanospores
only; spores cylindric filling the cells, 19-21 m x 37-70^; median spore
wall thick yellow-brown, scrobiculate, pits 1-3 i^i in diameter and 2-6 /a
apart, with several irregular sutures. (PI. VII, Fig. 10.)
South America, southern Chile.
87. Zygnema borzae Krieger 1941. Zygnemales. Rabenhorst's
Kryptoga?nenflora. 13, p. 264.
Vegetative cells 24-26/i. x 18-55/x; reproduction by aplanospores
only; aplanospores cylindric filling the sporangium wall, 14-27^ x
1 8-54 m; median wall thick, blue, punctate with irregular elongate and
variously curved pits 0.5/1 x i-2m in size. (PI. VII, Fig. 4.)
streams.
Rumania, Transylvanian Alps at 6,000 feet, attached to stones in