210 FRESH-WATER ALG^E OF TUE UKITBD STATES. 



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

 joints, their end joints alternate, ol'ten empty, eitlier not or scarcely piliferous; surrounded by a firm 

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



Remarhs. — 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. elegant, (Ruth) Agardii. 



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

 superficie hcvi vel quasi tubereulata, elastice niolli, nonnuncjuam indurato ; fasciculorum 

 ranuilis laxis vel confertis, articulis extremis brcvi-cuspidatis, sajpe piliferis. 



Syn, — C. elecjana, (Rotu) Agardii. Rabenuorst, Flora Europ. Algarum, Sect. III. p. 384. 



Hah. — United States. 



Thallus globose or suljglobose, 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 

 la.x or crowded ; end articles shortly cuspidate, often piliferous. 



Remarks. — One of the commonest of our fresh-water algaj is a plant belonging 

 to this genus, whicli I think is probably the C elegans of Roth. I am, how- 

 ever, unable to discover any characters separating C. pisiformis, G . ehgans, and 

 perhaps C. tuhcrcuJosa, 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. tuberculosa. 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 slipperiucss, 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 weU a young individual of this 

 species. 



C. endiTiaDFolia, (Roxn) Ag. 



Cli. thallo lineari, subplano, semipollicari vel pollicari, nonnunqnara valde clongato, la;te vel 

 obscure viridi, dichotoroo-subreticujatum-laciaiato (nonnunquara habitu Biccise Jluitarttis) ; 

 fills ramisque primariis plerumque achrois, passim viridi-zonatis, parallelis; ramulorura fasei- 

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

 diametro seqnalibus vel subaequalibus ; geniculis constrictis ; cytioplasmate granuloso 

 effuso. (R.) Species mihi ignota. 



Srjn. — C. endivixfolia, (Roth) Agardii. Rabenhorst, Flora Europ. Algarum, Sect. III. 

 p. 383. 



