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 CotnocHaAETaLes. 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 DesmipraLes. 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 EvpopiscaLes. Round Diatoms. Filaments com- 
monly cylindrical, usually fragmented 
into single cells. 
