ZYGOPHYCEAE 333 



Family 12. Trentepohliaceae. Scarcely attenuated, 

 no hairs, isogamic. — Trentepohlia. 



Family 13. Herposteiraceae. Scarcely attenuated, 

 with hairs, heterogamic. — Herposteiron. 



Family 14. Cylindrocapsaceae. Unbranched, hetero- 

 gamic. — Cylindrocapsa. 



Family 15. Oedogoniaceae. Unbranched or branched, 

 heterogamic. — Oedogonium. 

 Order Coleochaetales. Branched, fusing into discs, 

 heterogamic. 



1' amily 16. Coleochaetaceae. Minute disk-like 

 plants. — Coleochaete. 



Phylum III. ZYGOPHYCEAE. The Conjugate Algae 



ChlorophyU-green sluggish filaments, often fragmenting into 

 single ceUs 



Class 5, CONJUGATAE. Typically filamentous, green 

 plants, with cellulose walls. (Sp. 

 about 1,300.) 

 Order Ztgnematales. Pond Scums. Filamentous. 



FamUy 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, jNIicrasterias. 

 Class 6. BACILLARIOIDEAE. The Diatoms. Brownish- 

 green plants, with sUicified walls. 

 (Sp. about 5,700.) 

 Order Eupodiscales. Round Diatoms. Filaments com- 

 monly cyhndrical, usually fragmented 

 into single cells. 



