Plate II. 



FRESH-WATER ALG^. 



1. Spirogyrn, in conjugation 7. Vaucheria, Sexual reproduction : 



2. „ Zygospores formed in one filament x - Antheridium o. Oogonium 



3. „ Germination of zygospore z. Spermatozoids 



4. Vaucheria sessilis, branched filament S, 9, 10, 11, Vol-vox globator. See text. 



with root processes 12 to 19. Desmid. Cosmarium botryth 



5 „ Asexual reproduction ; zoospore Propagation by division (Figs. 13 to 15) 



escaping Sexual reproduction (Figs. 16 to 19j 



6. „ Zoospore free 20. Desmid. Closterium lunula 



21. Diatom. "Tinnularia \>iriJis 



