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



The only specimens that have come to my notice are in a dried condition, and 

 consequently no possible opportunity has been afforded of studying the manner of 

 reproduction. No one has as yet, at least to my knowledge, discovered any sexual 

 reproduction in the family, but the method in which the zoospores are produced 

 has been carefully studied, especially by Drs. Caspary (Regensburg Flora, 1858) 

 and Hildebrand (BotaniscJie Zeitung). The little motile bodies are not produced 

 in the cells indiscriminately, but in certain ones set apart for the purpose, to which 

 the name of zoosporangia is very applicable. These are large, globular, thick walled 

 cells, which are generally provided with a protuberance at the top and marked by 

 transverse wrinkles. They are most frequently situated upon the end of the filament 

 or one of its branches, but are rarely placed in the middle of the thread, and still 

 more rarely the cell next below the zoosporangium elongates itself sideways and up- 

 wards into a thread, so that the reproductive cell is left as a lateral one-celled branch 

 or process. When the zoosporangium is sufficiently matured the endochrome 

 breaks up into a number of minute masses, the future zoospores. Finally the 

 crowning papilla of the mother-cell ruptures and allows the contents to escape as 

 a well-formed vesicle, containing the perfected zoospores. It is said, however, that 

 sometimes the vesicle is wanting, and the zoospores are discharged into the water. 

 In the ordinary course, after a little while the vesicle lying in the water bursts 

 and sets its motile contents free. The zoospores themselves are very small, accord- 

 ing to Hildebrand, -g-f -^-^f u mm. in length, by ^ 5 g^mm. in breadth. In accord- 

 ance with the same authority they are, when first discharged, cylindrical, but in a 

 little while become flattened, and shaped like a flaxseed. They are biciliate and 

 contain a large number of small, orange-colored particles. From thirty-two to 

 sixty-four of them are formed in one zoosporangium, and neither light nor time of 

 day appear to have any influence upon their birth. Hildebrand states that their 

 motile life lasts from eighteen to thirty-six hours, but according to Caspary, after 

 continuing in motion for about an hour, they grow sluggish, sink, become globular, 

 then elongate themselves and shortly undergoing transverse division, actively com- 

 mence to form the new filament. 



Genus CHROOLEPUS, AG. 



Fila distincte articulata, intricata, enormiter raraosa. 

 Filaments distinctly articulate, intricate, irregularly branched. 



C. aureum, (.LINNE.) KTZ. 



C. filis ramossimis, in stratum aureo-brunneum, ad duas trcs lineas crassum, ccespitosum ct molle 



intricatis vel in caespitulos aggregatis ; articulis enormibus, diametro sesqui-, duplo triplove 



longioribus. 

 Diam. Max = .001". 



Syn. C. aureum, (LINNE.) KUTZINO. RABENHORST, Flora Europ. Algarum, Sect. III. p. 371. 

 Sab. Little Falls, New York ; Godwinsville, New Jersey ; (Austin). Texas ; (Ravenel). 



Filaments very much branched, interwoven to form a yellowish-brown softish mat, two or 

 three lines in thickness ; joints irregular, 1^-3 times longer than broad. 



Remarks. I am indebted to Mr. Austin for specimens which are labelled 

 " Forms dense yellow-brown cushions on rocks, at Little Falls, New York and 



