160 WISCONSIN PHYTOPLANKTON 



Sub-family COELASTREAE. 



Coenobia forming a sphere with the cells radially arranged in a single 

 layer around a common center. The number of cells in a coenoba al- 

 ways a multiple of two. Cells spherical, polygonal, or elongate cylindri- 

 cal. 



KEY TO THE GENERA. 



Cells spherical, polygonal, or flattened; length never more than twice the 

 breadth. 



Cells without spines on the outer face COELASTBUM 



Cells with spines on outer face SOBASTBUM 



Cells 3-7 times as long as broad ACTINASTBUM 



COELASTRUM Nageli 1849. 



Coenobe a hollow sphere of 2-4-8-16-32-64-128 cells. Cells spheri- 

 cal, ovoid, or pyramidal ; compressed or with large intercellular spaces ; 

 enclosed in a very delicate gelatinous sheath. Daughter coenobia some- 

 times remaining joined in multiple coenobia by the remains of the old 

 mother cell wall. 



Reproduction by autocolony formation in any cell of the coenobe. 

 Liberation of young coenobia by a rupture of old mother cell wall. 



KEY TO THE SPECIES. 

 Cells spherical. 



Processes uniting the cells long C. RETICULATUM 



Processes uniting the cells short. 



External face of cells without projections C. MICBOPOBUM 



External face of cells with short truncate projections. . .C. CAMBRICUM 

 Cells truncate cones C. PBOBOSCIDETTM 



COELASTRUM MICROPORUM Nageli. PL 41, Figs. 12-13; PL 42, Fig. 1. 

 in Braun, Alg. unicell. 70. 1855; Senn, Bot. Ztg. 57: 53, pi. 2, figs. 11-17. 1899. 



Coenobia spherical to ovoid ; with 8-16-32-64 cells. Cells spherical, 

 enclosed by a delicate gelatinous sheath and connected to one another 

 by short, stout, gelatinous processes. Intercellular interstices smaller 

 than the diameter of the cells. (Facultative Planktont). 



Diam. cells (without sheath) 3-20 /*; (with sheath) 4-23 p.. Diam. 

 coenobia 20-90 /A. 



Balsam (rrr), Bear (1) (rr), Bear (2) (rr), Bear Trap (rrr), Big Butter- 

 nut (rrr), Blake (rrr), Bone (rrr), Boulder (rrr), Browns (rr), Center 

 (rr), Chetac (rr), Cochrane (rr), Deer (rrr), East (rrr), Elizabeth (rrh 

 Fishtrap (rrr), Granite (rr), Hill (rr), Hillman (rrr), Horseshoe (2) (rrr), 



