STAUROGENIA. 171 



Diameter of well-grown specimens about 70 // ; often much 

 smaller, cells of a coeuobium in view, usually only ten. 

 Color light yellowish green, or colorless, except the young 

 coenobia in each cell, bright green. 



Ponds, not infrequent. 



Plate CLYI, fig. 5, a coenobium near maturity, the time 

 for yielding up the young plants. 



Genus 43, SOKASTRUM, Kg. 



Coenobium globose, solid within, free swimming, composed 

 of four, eight, sixteen or thirty -two compressed wedge-shaped 

 cells, which are sinuate, emarginate, or bifid at the apex and 

 radiately disposed. 



Propagation unknown. 



SORASTRUM SPINULOSUM, Kg. 



Coenobium globose, spinulose ; apex slightly emarginate, 

 angles obtusely rounded with two spines at each rounded 

 angle. Coenobia vary in diameter from 25-75 //. Cells 

 12-22 yu wide. 



The distinctive feature between this plant and those of 

 the last preceding genus is, that this forms a solid coenobium, 

 the others are hollow. 



More frequent than Coelastrum. 



Plate CLVI, figs. 6-10, smaller and larger coenobia, as 

 they differ in age ; fig. 10, differs more than the others, but 

 not sufficiently distinct for another species. 



Genus 44, STAUKOGENIA, Kg. 



Coenobium cubical, hollow within, composed of four or eight 

 or sometimes sixteen subquadrate cells. 



Propagation by quiescent gonidia, produced after the subdivi- 

 sion of the cell contents. 



Syn. Orucigenia, Morren. 



STAUROGENIA CRUCIATUM, Wolle. 



Coenobium consisting of four equilateral rhomboidal cells, 

 sides incurved, angles rounded, together forming a somewhat 

 square or rhomboidal figure. Cells united by a mucilagi- 

 nous deposit around or between them ; measure of coenobia, 



