30 GENERA OF ALG^E. 



n. Thallus soon diffluent into shapeless mucus, 



Tetraspora, 54, or Palmella, 56 

 n. Thallus with a definite form (o). 

 o. Cylindrical or compressed, branched, 2-12 inches long; one pole 



of cells colorless Hydrurus, 52 



o. Cylindrical, sometimes septate, attached at one end and spreading, 



Palmodactylon, 53 



o. Pear-shaped, fixed by the stem-like base .... Apiocystis, 76 

 /. Chlorophyll in spiral bands (g). 



p. Chlorophyll in two, many-rayed bodies in each cell (r). 

 p. Chlorophyll in axile plates (/). 

 q. Conjugation geniculate. Gulf States .... Sirogonium, 71 



q. Conjugation ladder-like Spirogyra, 70 



r. Conjugation ladder-like or lateral (s). 



s. Spore in one of the cells Zygnema, 72 



s. Spore in the connective between the cells . . . Zygogonium, 73 



/. Conjugation ladder-like (u). 



t. Conjugation lateral (v). 



t. Conjugation geniculate (w). 



t. Conjugation absent, spore formed spontaneously in the cell, 



Gonatonema, 78 

 u. Spore in the connective between the cells, 



Mougeotia,*]^, or Mesocarpus, 75 



u. Spores in one of the cells Plagiospermum, 77 



v. Spore lateral, at the point of two cells . . . Pleurocarpus, 76 

 w. Spore formed at point of conjugation . . . Crater ospermum, 80 

 w. Spore between the cells, quadrangular in front view, 



Staur ospermum, 79 



CLASS III. 



Multicellular or apparently so, filamentous (A). 

 Unicellular, the cells sometimes clustered or in families (V). 

 A. With hair-like points (B). 



A. Without " " (C). 



B. Branched (but spuriously so); in small tufts . . Calothrix, 81 

 B. Not branched; not in jelly mass; heterocysts yellow, at the base 



of the filaments; free or in small mats . . . Mastigonema, 82 



B. Not branched; in more or less firm mucilage or jelly (//). 



C. Branched; in a sheath or jelly mass (E). 

 C. Branched; not in jelly. 



C. Not branched (D). 



