210 FRESH-WATER ALGJi OF THE UNITED STATES. 



resolved into very numerous fasciculate, more or less densely congested branches, with shorter 

 joints, their end joints alternate, often empty, either not or scarcely piliferous ; surrounded by a firm 

 coriaceous or hard jelly, so as to form a globose, subglobose, or expanded thallus. 



Remarlcs. I have never seen the production of the zoospores in this genus, but 

 they are said to arise one in a cell, and to escape by a sort of lateral splitting of 

 the wall. 



C. elegans, (ROTH) AGARDH. 



Ch. thallo globoso vel subgloboso, pisi vel ccrasi magnitudine, dilute vel saturate viridi, nitido, 

 superficie Isevi vel quasi tuberculata, elastice molli, nonnunquam indurato ; fasciculorum 

 ramulis laxis vel confertis, articulis extremis brevi-cuspidatis, soepe piliferis. 



Syn. 0. elegans, (ROTH) AGARDH. RABENUORST, Flora Europ. Algarum, Sect. III. p. 384. 

 Hob. United States. 



Thallus globose or subglobose, of the size of a pea or cherry, light green, with the surface 

 smooth or quasituberculate, elastic but soft, sometimes indurated ; branches of the fasciculi 

 lax or crowded ; end articles shortly cuspidate, often piliferous. 



EemarJcs. One of the commonest of our fresh-water algae is a plant belonging 

 to this genus, which I think is probably the O. elcgans of Roth. I am, how- 

 ever, unable to discover any characters separating C. pisifdrmis, C. elegans, and 

 perhaps C. tuberculosa, and hardly know by which of the three names our Ameri- 

 can form should be known. Our plant grows generally in shaded pools, springs, 

 and ditches in great abundance, adhering as little translucent balls to grasses, 

 leaves, twigs, or anything that may be in the water. The size of the frond varies 

 from the young one, not so large as a pin's head, to the old matured one, which 

 may be nearly an inch in diameter. The color also varies greatly. It is always 

 some shade of a pure green. The surface is mostly smooth, but sometimes it is 

 so puckered up as to be a mass of large flat tubercles. It is these forms that I 

 suppose to represent C. tiiberculosa. The thallus is generally elastic, but at the 

 same time soft, so that although readily compressed and pushed out of shape, it is 

 entirely mashed with some difficulty, especially as, owing to its slipperiness, it 

 constantly escapes from the grasp. 



In regard to the individual filaments, the method of their branching and the 

 proportionate length and breadth of the cells vary very much in different in- 

 dividuals and probably at different ages of the same individual. 



Fig. 5, pi. 6, represents rather indifferently well a young individual of this 

 species. 



C. endiviaefolia, (ROTH) Ag. 



Ch. thallo linear!, subplano, semipollicari vel pollieari, nonnunquam valde elongate, hete vel 

 obscure viridi, dichotomo-subreticulatum-laciniato (nonnunquam habitu Ricciae fluitanlis) ; 

 filis ramisque primariis plerumque achrois, passim viridi-zonatis, para'llelis ; ramulorum fasci- 

 culis lateralibus, plus minus densis, divaricato-patentibus ; articulis plus minus tumidis, 

 diametro sequalibus vel subaequalibus ; geniculis constrictis ; cytioplasmate granuloso 

 effuso. (R.) Species mihi ignota. 



Syn. C. endiviaefolia, (ROTH) AGAHDH. RABENHORST, Flora Europ. Algarum, Sect. III. 

 p. 383. 



