1920] Setchell-Gardner : CMorophyceae 207 



13. Cladophora Kiietz. 



Plants composed of filaments of a single series of segments, the 

 filaments branching, usually abundantly ; branching lateral, but often 

 coming to appear dichotomous in consequence of the pushing aside of 

 the original filament by the branch ; growth in length chiefly by divi- 

 sion of the apical segment, subsequent division of segments being 

 rather exceptional ; branches all of the same type but different orders 

 usually differing in diameter; segments multinucleate, the chromato- 

 phore either covering the segment wall, or forming a network on it" 

 or in the form of numerous small disks; pyrenoids several in a seg- 

 ment ; reproduction by 4-ciliated zoospores, and by 2-ciliated gametes, 

 uniting and germinating immediately, or sometimes germinating 

 without copulation. 



Kuetzing, Phyc. Gen., 1843, p. 262. 



The genus Cladophora was established by Kuetzing in 1843, the 

 same year that Hassall (1843, p. 363, May) proposed the genus 

 Microspora to include the branching species of the old genus Conferva. 

 It is possible that Microspora Hassall antidates Cladophora Kuetzing, 

 but Hassall (1845, p. 213) withdrew his genus and adopted that of 

 Kuetzing. The name Microspora was later used by Thuret (1850, 

 p. 221) to designate a later segregation from Conferva and this name 

 is still current in the sense indicated by Thuret. 



The type species of Kuetzing 's genus is the C&nferva oligocloim 

 Kuetzing (1833, no. 62), a fresh -water species and there is little ques- 

 tion as to the limits of the genus, except possibly towards some of its 

 segregates. It is distinctly and readily separated from Chaetomorpha 

 by its branching and from Rhizoclonium by the method of its branch- 

 ing. The difficulties of separating Spongomorpha Kuetz., Aegagropila 

 Kuetz. and Acrosiphonia J. Ag., if it seems best to do so, are at times 

 considerable. The species of all these genera are of more spongy 

 habit than are those of the true or typical Cladophora. In Spongo- 

 morpha and Acrosiphonm the spongy condition is brought about by 

 specialized rhizoidal or spinelike branches which hold the mass of 

 branches together. In Aegagropila, there are no such specialized 

 branches and it has seemed best to us not to separate the species of 

 Aegagropila from those of Cladophora. The distinction between the 

 two genera depends largely upon habit and is not always applicable 

 with certainty and precision. 



