322 TUFTS COLLEGE; STUDIES, VOL. II, No. 3 



with chromatophore net-form, or broken into many small por- 

 tions, with many pyrenoids ; asexual reproduction by 4-ciliate 

 zoospores (sometimes by biciliate?) and by akinetes ; sexual 

 reproduction by biciliate gametes; zoospores and gametes 

 formed in little changed vegetative cells. Marine and fresh 

 water. 



KEY TO THE GENERA OF CLADOPHORACEAE. 



i. Filaments simple. 2. 



I. Filaments branched: 3. 



2. Filaments firm, stiff. 12. 



2. Filaments soft, flaccid. 12. HORMISCIA. 



3. Branches free, not united to form a membrane or tissue. 4. 



3. Branches united to form a membrane or tissue. 8. 



4. Branches usually short, rhizoidal. 2. RHIZOCLONIUM. 



4. Branches of successive orders, but of the same character. 5. 



5. Partitions regularly at bases of branches. 6. 



5. No partitions regularly at bases of branches. 



5. CLADOPHOROPSIS. 



6. Akinetes formed of swollen intercalary or terminal cells ; zo- 

 ospores unknown. 6. PITHOPHORA. 



6. Akinetes unusual, little differentiated ; propagation by zoospores. 



7- 

 7. Specialized hooked or rhizoidal branches present ; cell division 



largely intercalary. 4. SPONGOMORPHA. 



7. No specialized hooked or rhizoidal branches ; cell division chiefly 



terminal. 3. CLADOPHORA. 



8. Filaments united in one plane. 9. 



8. Filaments united in all directions, forming a solid or spongy 



frond. ii. 



9. Frond continuous. 7. ANADYOMENE. 



9. Frond perforate. 10. 



10. Small secondary cells formed in the spaces between the filament 



cells, leaving rounded openings. 9. CYSTODICTYON. 



10. No such secondary cells ; openings angular. 



8. MlCRODICTYON. 



ii. Frond a spongy mass of network. 10. BOODLEA. 



ii. Frond spherical, solid or hollow. ii. DICTYOSPHAERIA. 



12. Filaments regularly cylindrical or clavate ; originally attached, 



sometimes later floating. i. CHAETOMORPHA. 



12. Filaments usually more or less irregular ; not attached. 



2. RHIZOCLONIUM. 



i. CHAETOMORPHA Kutzing, 1845, p. 203. 

 Frond of a single unbranched series of multinucleate cells, all 

 but the usually longer basal cell capable of division ; basal cell 

 producing either a disk or more or less branched rhizoidal pro- 



