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



it appears that from each gonidium there runs to each of the six 

 surrounding ones a fine thread, sometimes double, always of ex- 

 treme tenuity, and often so delicate as not to be seen at all, 

 except by the use of reagents which often bring these lines into 

 view, where it had been impossible to detect them. 



VOL vox GLOBATOR, Linn. 



Larger coenobia with very numerous cells, (gonidia) 

 always with daughter-coenobia enclosed within the maternal 

 one, evolved without sexuality ; fructification monoecious ; 

 oogonia and antheridia developing in the same coenobium. 

 The oogonia are often numerous. 



Diameter of well developed coeiiobia, often 650 JJL. 

 Diameter of vegetative cells, 2-3 jw. 

 Diameter of oogonia about 50 //. 

 Diameter of antheridia about 35 /*. 

 Diameter of spermatozoids, 4-6 yu long. 



Plate CLI, figs. 1-4, different stages of development, the 

 latter with encysted resting spores. 



Plate CLII, fig. 1, coenobium showing the fine threads 

 connecting the gonidia ; fig. 2, enlarged figure of connecting- 

 threads ; fig. 3, an ideal section of the wall of a coenobium, 

 showing the gonidia, flask-like, imbedded, with ciliated 

 ends ; basal parts often developing oogonia and antheridia ; 

 fig. 4, coenobium with three stellate resting spores ; fig. 5, 

 a stellate oogoniurn or resting spore ; fig. 6, an exaggerated 

 ideal of a section of a coenobium illustrating the ciliated 

 ends of the gonidia extending through the gelatinous en- 

 velope ; two oogonia dividing, a stellate resting spore and 

 two undeveloped oogonia ; fig. 7, a complete antheridium, 

 after "Wills ; figs. 8, 9, spermatozoids. 



Much disparity of opinion and uncertainty prevail regard- 

 ing the mode of fructification ; some maintaining they are 

 monoecious and others dioecious. 



VOL vox AUREUS, Ehrb. 



These are larger spherical cells, surrounded by a thick, 

 smooth, colorless, often lamellate epispore, found within a 

 mother coenobium ; probably merely resting spores. 



Plate CLI, fig. 4, six such resting spores. 



VOLVOX STELLATUS, Ehrb. 



Stellate forms are sometimes very numerous in a coeno- 

 bium, varying in number from ten to one hundred and more 



