WISCONSIN PHYTOPLANKTON 85 



BOTRYOCOCCUS PROTRUBEBANS var. MINOR G. M. Smith. PL 15, Figs. 6-7. 

 Trans. Wis. Acad. Sci., Arts, & Lett. IV: 652, pi. 14, figs. 6-7. 1918. 



Cells in colonies of 4-8-16 or more held together by a tough gelat- 

 inous membrane. Colonies frequently joined to one another by long 

 hyaline strands of the colonial envelope. Cells ovoid to cuneate-ovoid, 

 with their bases embedded in the colonial envelope and their apices 

 not enclosed by the envelope. Cells arranged in a single layer around 

 a central cavity. Chromatophores single, yellowish-green, laminate, 

 occupying the median portion of the cell. (Euplanktont). 



Cells 8-9.5 p. long, 5-6.5 p. broad at the widest part. 



Diamond (rrr), George (aa), Hillman (rr), Lindy (rr), Oak (ss), Pardee 

 (rr), Sanford (rr), South Crab (s). 



This species is distinguished from the foregoing by the smaller num- 

 ber of cells in the colony and the projection of the apex of the cells 

 through the colonial integument. 



Family OPHIOCTTIACEAE. 



Cells sessile or free-floating, solitary or colonial. Length of cells 

 generally several times the breadth. Cells straight, curved, sigmoid, or 

 spiral; with or without terminal spines. Chromatophores yellowish- 

 green ; annular, parietal and few in number ; or discif orm, parietal and 

 numerous ; without pyrenoids and with oil as the assimilation product. 



Asexual reproduction by division of cell contents to form 4-16 aplano- 

 spores or 2-8 biciliate zoospores with cilia of unequal length. 



Sexual reproduction unknown. 



OPHIOCYTIUM Nageli 1849. 



Cells free-floating or epiphytic, solitary or colonial ; straight, arcuate, 

 sigmoid, or spiral elongate cylinders with rounded or capitate ends 

 that may be apiculate or attenuated into a single spine. Chromato- 

 phores pale yellowish-green, H-shaped in optical cross section, without 

 pyrenoids and with oil as the assimilation product. Cells coenocytic. 

 Cell wall consisting of a homogeneous cap at one end and with the re- 

 maining portion of the wall composed of a number of laminate layers. 



Asexual reproduction by division of cell contents to form 416 aplano- 

 spores or 2-8 biciliate zoospores with cilia of unequal length. 



