82 WISCONSIN PHYTOPLANKTON 



Family CHLOROBOTRYDACEAE. 



Cells solitary or in free-floating colonies enclosed by a copious, homo- 

 geneous, gelatinous envelope. Colony generally with a small number 

 of cells and with cell number a multiple of two. Cells spherical, ovoid, 

 angular, or cylindrical ; with a firm cell wall that is sometimes impreg- 

 nated with a slight trace of silica ; and with one to many parietal, disci- 

 form, yellowish-green chromatophores without pyrenoids. 



Asexual reproduction by vegetative cell division or a formation of 

 zoospores with two cilia of unequal length. 



CHLOROBOTRYS Bohlin 1901. 



Cells rarely solitary, generally in colonies of 2-4-8-16 or more em- 

 bedded in a copious, homogeneous, hyaline, gelatinous envelope. Cells 

 spherical to broadly ovoid, with a heavy wall that sometimes contains 

 a small amount of silica. A conspicuous red pigment spot present in 

 cells at times. 



Reproduction by vegetative division of cells in three directions. 



KEY TO THE SPECIES. 



Cells ovoid, with few chromatophores C. L.IMNETICUS 



Cells spherical, with numerous chromatophores C. REGULABIS 



CHLOROBOTRYS REGULARIS (W. West) Bohlin. PI. 15, Fig. 10. 



Bih. kgl. Sv. Vet.-Ak. Handl. 27, Afd. 3, No. 4: 34. 1901; W. & G. S. West, 

 Jour, of Bot. 41 : 78, pi. 447, figs. 7-10. 1903. 



Chlorococcum regulare W. West, Jour. Roy. Micr. Soc. 1892: 737, pi. 10, 

 fig. 55. 1892. 



Cells spherical to subspherical ; rarely solitary, generally in colonies 

 of 2-4-8-16 enclosed by a copious, hyaline, homogeneous, gelatinous 

 envelope. Cell wall thick, sometimes containing a trace of silica. 

 Chromatophores yellowish-green, disciform, parietal, 6-30 in each cell. 

 Cells at times containing a single conspicuous red pigment spot. (Ty- 

 choplanktont). 



Diam. cells 10-27 p. Diam. colonies 35-90 /*. 



North Turtle (rrr). 



CHLOROBOTRYS LIMNETICUS G. M. Smith. PI. 15, Fig. 9. 

 Trans. Wis. Acad. Sci., Arts, & Lett. 19 1 : 653, pi. 14, fig. 10. 1918. 



Cells ovoid, irregularly distributed within a homogeneous, hyaline, 

 gelatinous envelope. 10-30 cells in a colony. Chromatophores 3-4, 



