330 FRESH-WATER ALG^E OF THE UNITED STATES. 



Genus 117, POLYCYSTIS, Kg. 



Cellules globose, united into spherical families which cluster 

 together, grape-like. 



POLYCYSTIS ICHTHYOBLABE, Kg. 



Thallus membranous, aeruginous, or with a reddish tinge ; 

 cells globose, crowded, with light aeruginous contents. 

 Families usually about 50 yu ; sometimes as large as 1 10 /* 

 diameter. 



Diameter of cells, 2-3 /*. 



Not frequent ; occasionally in small pools. 

 Plate OCX, fig. 24, a small cluster of family-cells. 



Genus 118, GLOEOCAPSA, Naeg. 



Cells usually spherical, or before division somewhat oblong, 

 with wide vesiculiform tegument, this cell undergoing division 

 into two daughter cells. Each has a distinct tegument, the whole 

 being surrounded by the tegument of the mother cell. This 

 process is often repeated, the original tegument remaining and 

 surrounding the family thus formed. Cell membrane often very 

 thick, mostly lamellated ; strata not infrequently separating ; 

 colorless or colored ; cell contents aeruginous, bluish green, steel 

 blue, reddish, yellowish, fuscous, etc. Division in three direc- 

 tions. 



Eabenhorst, in his Flora Algarum, describes more than sixty 

 forms as species and varieties. These unicellular forms are very 

 changeable in color and in details of construction, number and 

 size of cysts. The same cells may be at one time aeruginous, 

 then change to a light yellow or orange color ; or crimson or 

 scarlet. Sometimes they form a crustaceous stratum, and then 

 they occur in soft gelatinous masses, so abundant, they may be 

 stripped from dripping, partially shaded rocks, by handfuls. 

 Occurring in so many different conditions, and varying so much 

 under different circumstances, it may be readily conceived how 

 the many stages of development, found at different times and by 

 different persons, gave rise to the record of the many forms as 

 species. 



It is now clearly evident that all of these so-called unicellular 

 plants constitute nothing more nor less than conditions in the 

 plant-life of higher forms. This fact has already been shown 

 under the head of Sirosiphon ; also illustrated on Plates CXC ; 

 CXCI; CXCIV 5 CXCV. They are the spores, or macrogonidia 



