42 



Fresh-water Biology 



{Continued frofn page 40) 



11 — Filaments not attenuated and hair like at the ends 12 



— Filaments conspicuously attenuated towards one or both ends. Rivulariaceae. 

 Filaments each with a basal heterocyst; filaments radiating in a gelatinous mass 

 (Fig. 7), Rivularia, Gleotrichia. Several other genera. 



12 — Filaments usually not branching; where they show branching there are not hetero- 



cysts 13 



— Filaments branching. True branching, Stigonemaceae; false branching, heterocysts 

 present Scytone maceae 



13 — Cells of the filaments all of uniform size; without heterocysts. — Oscillatoria- 



ceae 14 



— Filaments with occasional cells of different color or larger size (heterocysts) Nosxo- 

 caceae 18 



14 — Filament without a sheath 15 



— Filament enclosed in a gelatinous sheath 16 



15 — A single spiral cell (fig. 12) Spirulina 



— Multicellular. Filament a spiral, Arthrospira; not a spiral (fig. 5). ( = Oscillatoria) 

 Oscillaria 



{Continued on page 44) 



Plate 17. Blue-Greens 



"*-n — n 



oooo 

 oooo 

 oooo 

 oooo 



6 



'bo: 



,°o 



%o 



p 



Oo 



OO-O'-n^o'O/ 

 O O n oV_ 



^^^' I Q 



1, Phormidium 



2, Tetrapedia 



3, Aphanizomenon 



4, Anabaena 



5, Oscillatoria 



6, Merismopedia 



1, 2, Pediastrum 



3, Kirchnerjella 



4, Dictyosphferium 



5, Characium 



6, Bulbochtete 



7, Selenastrum 

 8, 9, Coelastrum 



10, Botryoccoccus 

 11, 12, Ankistrodesmus 



13, Richteriella 



14, Scenedesmus 



15, Ophiocytium 



16, Sorastrum 



17, Spirogyra 



7, Rivularia 

 8, 9, Microcystis 



10, CcElosphaerium 



11, Nostoc 



12, Spirulina 



13, Aphanocapsa 



Anabaena, 4 

 Aphanocapsa, 13 

 Aphanizomenon, 3 

 Coelosphaerium, 10 

 Merismopedia, 6 

 Microcystis, 8, 9 



Plate 18. Green Algae 



18, 19, Mougeotia 



20, Zygnema 



21, Tetraspora 

 22, 23, Pleurococcus 



24, Cladophora 



25, Hydrodictyon 



26, Crucigenia 



27, Chastophora 



28, Microspora 



29, Ulothrix 



30, Oedogonium 



31, Tribonema 



32, Draparnaldia 



Ankistrodesmus, 11, 12 

 Botryoccoccus, 10 

 Bulbochaete, 6 

 Characium, 5 

 Chaetophora, 27 

 Cladophora, 24 

 Coelastrum, 8, 9 

 Crucigenia, 26 

 Dictyosphaerium, 4 

 Draparnaldia, 32 

 Hydrodictyon, 25 

 Kirchneriella, 3 

 Microspora, 28 



Nostoc, 11 

 Oscillatoria, 5 

 Phormidium, 1 

 Ricularia, 7 

 Spirulina, 12 

 Tetrapedia, 2 



Mougeotia, 18, 19 

 Oedogonium, 30 

 Phiocytium, 15 

 Pleurococcus, 22, 23 

 Pediastrum, 1, 2 

 Richteriella, 13 

 Scenedesmus, 14 

 Selenastrum, 7 

 Sorastrum, 16 

 Spirogyra, 17 

 Tiibonema, 31 

 Ulothrix, 29 

 Zygnema, 20 



