WISCONSIN PHYTOPLANKTON 147 



quently irregular. The gelatinous sheath enclosing the colony is very 

 delicate and can only be seen when properly stained. This species was 

 placed in the genus Tetrastrum in a preliminary list, but it is more 

 closely related to Crucigenia than to Tetrastrum. 



CRUCIGENIA QUADRATA Morren. PI. 36, Figs. 10-14. 



Ann. Sci. Nat. 20: 415, pi. 15, figs. 1-5. 1830. 



Staurogenia triangularis Chodat, Mem. Herb. Boiss. 1, No. 17: 7, figs. 14-19. 

 1900. 



Crucigenia triangularis (Chodat) Schmidle, Allg. Bot. Zeitschr. 6: 234. 1900. 



Staurogenia multiseta var. punctata Schmidle, Ber. d. D. bot. Ges. 18: 157, 

 pi. 6, figs. 13-14. 1900. 



Coenobia four-celled, circular in outline. Cells in mutual contact at 

 or with very small rectangular openings at center of the coenobe. 

 Four coe'nobia compressed to form rectangular multiple coenobia which 

 in turn are joined to other sixteen-celled multiple coenobia. Cells 

 spherical to triangular; with a smooth wall or with 1-6 minute knob- 

 like projections on the wall. Chloroplasts 1-4, parietal, disciform, with 

 or without pyrenoids. (Facultative Planktont) . 



Cells 2.5-6 p. broad, 3-7 /* long. Coenobia 5.5-17 p. in diam. 16- 

 celled compound coenobia 12-30 /* in diam. 



Carson (rrr), Chain (rr), Hillman (sss), Kitten (rrr), Lac du Flambeau 

 (IT), Palmer (sss), Pardee (rr), Tenderfoot (rrr), White Sand (rrr). 



Pyrenoids are very prominent in the chloroplasts of certain colonies 

 while other colonies collected from the same station show no trace of 

 them. In some of the colonies from Hillman lake small, globular, but- 

 ton-like structures were observed on the cell walls. Such structures 

 have been noted by Schmidle and form the distinctive character of his 

 variety punctata of Staurogenia multiseta [Tetraslrum multisetum 

 (Schmidle) Chodat]. If the variety is to be recognized it should be 

 called C. quadrat a var. punctata (Schmidle) but I am of the opinion 

 that it is not a sufficiently constant character to warrant recognition. 

 There is likewise no justification for considering C. triangularis (Cho- 

 dat) Schmidle a distinct species since it does not differ in any respect 

 from C. quadrata. 



CRUCIGENIA TETRAPEDIA (Kirchner) W. & G-. S. West. PI. 37, Fig. 2. 



Trans. Roy. Irish Acad. 32, Sec. B: 62, pi. 1, figs. 11-12. 1902. 



Staurogenia tetrapedia Kirchner, Jahreshefte d. Ver. f. Vaterl. Naturk. i. 

 Wiirttemberg 1880, pi. 2, fig. 1. 



Tetrapedia emarginata Schroder, Ber. d. D. bot. Ges. 15: 492, pi. 25, figs. 

 6a-6c. 1897. 



Lemmermannia emarginata (Schroder) Chodat, Mem. Herb. Boiss. 1, No. 

 J7; 5, figs. 1-8. 1900. 



