328 FRESH-WATER ALGvE OF THE UNITED STATES. 



GOMPHOSPHAERIA APONIA, Kg. 



Thallns microscopical, at first light, or darker aeruginous, 

 but soon fades or changes to a yellow, or orange color, (var. 

 aurantiaca, Bleisch). 



Diameter of cells about 4 yw ; length, 10 ^ ; diameter of 

 family, 50-75 yw. 



Frequent in small pools. 



Plate OCX, fig. 20, two developed forms ; figs. 21, 22, 

 young conditions. 



Genus 115, MICKOCYSTIS, Kg. 



Cells very small, numerous, densely aggregated into globose 

 bodies, surrounded by a thin membrane, forming families, 

 usually single, but rarely several surrounded by a universal 

 tegument ; cell division in three directions alternately. 



A condition of frequent occurrence in the process of develop- 

 ment of higher forms, specially of Scytonema and Sirosipkon. 



MICROCYSTIS PROTOGENITA, (Bias. ) Eab. 



An old name which may be applied to various forms 

 which would come under this genus. The families are ordi- 

 narily subspherical, measuring from 15-75 yu in diameter. 

 Cells, which crowd the teguments more or less, are 4-6.5 /* 

 in diameter ; in color primarily aeruginous, but changeable 

 to light yellow, to orange, and sometimes to purple. 



Occurring on moist timbers, outside of old water tanks, 

 moist ground, and trunks of trees. All of them are evi- 

 dently mere conditions of development of higher plant-life. 

 Confer with figures of Scytonema and ftirosiphon, Plates 

 CLXXXVII; CLXXXVI; CXCI. 



. * Plate OCX, fig. 23. 



Genus 116, ANACYSTIS, Menegh. 







Cells spherical, innumerable in mucous strata ; primarily the 

 cells are enclosed in smaller families, by very delicate teguments 

 which quickly dissolve, and are only rarely visible. 



The forms of the present genus differ from those of the last 

 ( Microcystis ) in not having the families so distinctly separated, 

 and enclosed in so firm teguments. The former are solitary or 

 gregarious, the latter are united, massed together. The former 

 is easily traceable in its life-history ; the latter is very uncertain. 



