Synopsis of Genera 189 



Sexual reproduction through conjugation of gametes similar in 

 character, though sometimes differing in size. 



Synopsis of Tribes and Genera 



Tribe I. Chaetophoreae 

 Plants attached at the base, erect, extensively branched, with more or less differentiation 

 of supporting and reproductive portions (except in Microthamnion) . All fresh- 

 water plants. 

 Plants less than I mm. high, not setiferous. I. Microthamnion. 



Plants larger, branches generally pointed or setiferous. 



Filaments fine, showing little difference in character of stem and branches. 



II. Myxonema. 

 Filaments fine, in tufts involved in dense gelatinous substances. 



III. Chaetophora. 

 Filaments and main branches larger, bearing dense fascicles of small branchlets. 



IV. Draparnaldia. 



Tribe II. Herposteireae 

 Plants microscopic, creeping on or within other algae or animals, without distinction 

 between basal and apical cells, and without differentiation of supporting and 

 reproductive portions. 

 Inhabiting salt water. 



Plants tending to form an expanded thallus, growing on the surface of bryozoa. 



V. Epicladia. 

 Plants simply branched, endophytic within the membrane of Elachista. 



VI. Endoderma. 

 Plants bearing special setiferous cells, epiphytic on Phaeophyceae. 



VII. BOLBOCOLEON. 



Inhabiting fresh water. 



Plants composed of flask-shaped cells, bearing setae sheathed at the base. 



VIII. Chaetosphaeridium. 

 Plants composed of globose or cylindrical cells, bearing setae bulbous at the 

 base. IX. Herposteiron. 



The genera of the Chaetophoreae are rather closely related, 

 though Microthamnion and Myxonema, which are placed together, 

 probably had a separate origin. The latter might be naturally 

 derived from Ulothrix, while the former may have developed from 

 a small Stic/iococcus-\ike ancestor. Cliaetophora and Draparnal- 

 dia may easily be conceived of as developing from Myxonema. 



The genera of the Herposteireae are a somewhat heterogeneous 

 group, and perhaps have originated in different ways from proto- 

 coccoid ancestors. Only Epicladia and Endoderma are closely 

 related morphologically. Herposteiron seems to approach most 

 nearly to the Coleochaetaceae, for it is not a great step from the 



