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; Mich- 

 igan; 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 chro- 

 matophores; 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' s 



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?nen flora. 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.) 



Rumania, Transylvanian Alps at 6,000 feet, attached to stones in 

 streams. 



