Fig. 6. a) Nostoc sp.; b) Anabaena sp.; c) Cyllndrospermum sp.
   The pale blue-green gelatinous bean-sized colonies of Nostoc are sometimes found In great abundance In clear spring-fed lakes. If they could be kept permanently they would rival pearls for beauty.

   8b) Filaments gradually tapering to one or both ends.
Family RIVULARIACEAE

   Fig. 7. a) Sacconema rupestre Borzl.; b) Rivularla sp.
   Colonies of Rivularla are often arranged with the basal ends of the filaments standing at the center of a sphere and the whlpllke ends radiating to the circumference. Such balls are frequently 2 or 3 mm. In diameter.

   9a) Filaments with false branches; enclosed in a sheath.
Family SCYTONEMATACEAE

   Fig. 8. a) Scytonema sp.; b) Tolypatrix sp.
   False branching is characteristic of several groups of algae. It's something like propaganda or stealing 2nd base;-you must look close to see exactly what goes on.

   9b) Filaments with true branches; sheathed; often more than one cell in diameter.
Family STIGONEMATACEAE

   Fig. 9. Stigonema turfaceum Cooke.
   The members of this genus grow in damp soil or in fresh water and are fairly common.

   10a) Algae that are bright "grass-green" in color. Figs. 10 to 52

   10b) Algae with red, brown or yellow pigments more or less maskiIng the green chlorophyll. Figs. 53 to 116

   11a) Plant fine; relatively small. Figs. 11 to 52.

   11b) Plant coarse, at least a few inches long, branched, with nodes from which arise whorls of cylindrical leaves which in turn bear leaflets; sometimes encrusted with lime.
Order CHARALES Family CHARACEAE

   Fig.10. Chara fragalls Derv. a) branch of plant; b) reproductive organs.
   This is the only family of its order and class and has comparatively few species though they are fairly common and widely distributed. These plants are so different from all other green algae that they have been given a phylum of their own. These plants attain a height of several Inches and are quite complex in their structure. Reproduction Is always sexual. Nitella is another common genus.

   12a) Naked free-swimming cells with one, two or rarely more whip- like flagella at the anterior end. Some species are colonial. (Some have a non-motile encysted stage.) Sexual reproduction unknown. Figs. 11 to 14

   12b) Microscopic single celled plants to large thallus-like plants with cellulose walls. The flagella of motile forms usually number 2 or 4, and are equal in length. Most species of the phylum have sexual reproduction. Figs. 15 to 52 16

   13a) Cells non-motile and living attached to crustaceans and rotifers in indefinite masses or branching colonies.
Family COLACIACEAE