SPIROGYRA 151 



3. Spirogyra juercensii Kiitzing 1845. Phycologia Germanica, 



p. 222. 



Vegetative cells 24-30 /a x 60-125 /a, with plane end walls; i chro- 

 matophore, making 2 to 4 turns; conjugation scalariform and lateral; 

 tubes formed by both gametangia; fertile cells cylindric or enlarged 

 toward the middle (to 34^); zygospores and aplanospores eUipsoid, 

 28-33 M X 50~75^-; median spore wall yellow, smooth. (PI. I, Fig. i; 

 PI. XXI, Fig. 3.) 



United States: California; from Wisconsin, Iowa, and Texas to the 

 east coast. 



Widely distributed in Europe; South America; Australia. 



Distinguished from S. longata by the ellipsoid spores. Sometimes at 

 maturity the stretching of the fertile cell wall shortens that end of the con- 

 jugating tube, and the tube has the appearance of having been formed by 

 the male cell as in S. punctijormis and S. micropunctata. From the former 

 it is distinguished by the ellipsoid, smooth spores; from the latter by the 

 smaller size and smooth spore wall. In a collection from Mississippi cylin- 

 drically inflated akinetes with thick walls were present together with zygo- 

 spores. The dimensions of the akinetes varied from 48-60 ju x 108-140 /.i. 

 (PI. I, Fig. I.) 



4. Spirogyra singularis Nordstedt 1880. Bot. Notiser 1880. 



p. 118. Wittrock and Nordstedt Algae Exsiccatae, No. 361. 



Vegetative cells 29-39^1 x 60-240 /x, with plane end walls; i chro- 



matophore, making 3 to 7 turns; conjugation scalariform; tubes formed 



by both gametangia, fertile cells cylindric, rarely enlarged; zygospores 



elHpsoid, 27-36 jn x 46-70 jU,; median spore wall yellow, smooth. (PI. XXI, 



Fig- 4-) 

 ■ United States: Michigan and Texas, to the east coast. 



Described from New Zealand; reported from Finland; South Africa; 

 China; Brazil. 



Distinguished from S. longata by the ellipsoid spores. In all specimens 

 seen the chromatophores were narrow and the spirals very open. 



5. Spirogyra silvicola Britton 1943. Amer. Jour. Bot. 30, p. 799, 



Fig. I. 



Vegetative cells 32-42 m x 63-267 ju., with plane end walls; i chro- 

 matophore, making 1.5 to 3 turns in the cell; conjugation scalariform; 

 tubes formed by both gametangia; receptive gametangia cylindric or 

 slightly enlarged; zygospores ellipsoid to cylindric-ovoid, 36-43 /a x 

 56-103 /a; all walls smooth; median wall yellow or brown at maturity. 

 (PL XXI, Fig. 7.) 



United States: Illinois, Somme Forest, Cook County, May 15, 1938 

 (Britton Coll.); Texas, Austin (Taft Coll.). 



Vegetative cells similar to those of S. singularis; zygospores much larger. 



