ZYGOPHYCEAE 333 



Family 12. Trentepohliaceae. Scarcely attenuated, 



no hairs. Trentepohlia. 

 Family 13. Herposteiraceae. Scarcely attenuated, 



with hairs. Herposteiron. 

 Family 14. Cylindrocapsaceae. Unbranched, hetero- 



gamic. Cylindrocapsa. 

 Family 15. Oedogoniaceae. Unbranched or branched, 



heterogamic. Oedogonium. 



Order COLEOCHAETALES. Branched, fusing into discs. 

 Family 16. Coleochaetaceae. Minute disk-like 



plants. Coleochaete. 



Phylum III. ZYGOPHYCEAE. The Conjugate Algae 



Chlorophyll-green sluggish filaments, often fragmenting into 

 single cells 



Class 5. CONJUGATAE. Typically filamentous, green 

 plants, with cellulose walls. (Sp. 

 about 1,300.) 

 Order ZYGNEMATALES. Pond Scums. Filamentous. 



Family 1. Mesocarpaceae. Chloroplast single, long, 



axial. Mougeotia, Gonatonema. 

 Family 2. Zygnemataceae. Chloroplasts two, short, 



axial. Zygnema, Zygogonium. 



Family 3. Spirogyraceae. Chloroplasts 1 to 9, parie- 

 tal, spiral. Spirogyra. 

 Order DESMIDIALES. Desmids. Filaments usually early 



fragmenting into single cells. 



Family 4. Desmidiaceae. Unbranched filaments. 



Genicularia, Hyalotheca, Desmidium. 



Family 5. Closteriaceae. Cells solitary, elongated. 



Closterium, Penium. 



Family 6. Cosmariaceae. Cells solitary, broad, flat- 

 tened. Cosmarium, Micrasterias. 



Class 6. BACILLARIOIDEAE. The Diatoms. Brownish- 

 . green plants, with silicified walls. 



(Sp. about 5,700.) 



Order EUPODISCALES. Round Diatoms. Filaments com- 

 monly cylindrical, usually fragmented 

 into single cells. 



