164 FRESH-WATER ALG^ OF THE UNITED STATES. 







This interesting little plant was first observed in Germany 

 in 1850, and since in many places including the British Isles. 

 Presumably it will be discovered in this country also. In 

 anticipation, have quoted the above from European works. 

 Prof. Cohn made exhaustive examinations and studies of 

 the life-history of Stephanosphaera and has prepared able 

 memoirs, the first of which appeared in Liebold & Kolliker's 

 Zeitschri/t fur Zoologie, 1852 ; the other in Nova Acta Acad. 

 Leop. Cur., 1857, part I, vol. XXVI, to which the student is 

 referred for full particulars. The same author has also given 

 an excellent paper on the previous genus, Gonium, in the 

 Xova Acta, vol. XXIV, p. 169. 



Plate CLI, fig. 11, polar view of family with globose 

 primordial cells ; fig. 12, lateral view, with fusiform prim- 

 ordial cells ending in mucous filaments ; fig. 13, commence- 

 ment of formation of macrogonidia ; fig. 14, division of 

 macrogonidia advancing so that each cell consists of eight 

 cuneate segments. 



Genus 38, CHLAMYDOCOCCUS, A. Br. 



Cells globose, or subglobose, (4-8 joined in a very fugitive 

 coenobium ) cell membrane thickish, firm ; cell contents granular, 

 brownish red or vermilion, in certain stages changing into green, 

 or partially green with red center. Macrogonidia 2-4-8 rounded, 

 the frontal extremity bearing long cilia, containing 4-6 starch 

 granules, (not always visible,) involved in an ample, hyaline, 

 mostly ovoid tegument. Microgonidia much smaller, numerous, 

 .yellowish or dull green, the apex reddish, biciliate, moving 

 actively within the mother cell, and at last escaping by rupture 

 of the membrane. 



CHLAMYDOCOCCUS PLUVIALIS, A. Br. 



Cells subglobose, very variable in size; brownish red, 

 changing in some conditions to green. 



Diameter of cells, 7-40 yw. 



Perhaps no plant is more Proteus-like than this little 

 form ; normally sometimes like a plant, and sometimes like 

 an animal ; ordinarily it presents the appearance of small 

 globules, with a thick, tough, granular or punctate cell- 

 membrane; cell contents opaque, of a brown, reddish- 

 brown, or red color ; found in small pools of rain water. 



Dr. F. Cohn devoted two years of his time to a full com- 

 prehension of the life-history of this species ; he, adopting 

 the name of Protococcus pluvialis, prepared an elaborate 



