2 Minnesota Algae 



reproduction by vegetative division of cells in one, two or three directions 

 of space. 



Family II. Chamaesiphonaceae. Plants often shoviring a difference be- 

 tween basal and apical regions, solitary or associated in families or col- 

 onies, usually epiphytic or attached to shells;, reproduction by means of 

 non-motile gonidia formed by the division of the contents of a mother cell 

 (gonidangium). 



Family I. CHROOCOCCACEAE 



I. Plants solitary or associated in small, indefinite families or colonies, 



not surrounded by a common (colonial) gelatinous tegument. 



1 Cells spherical; reproduction by cell division in three directions 



Chroococcus 



2 Cells spherical; reproduction by cell division in one direction only 



Synechocystis 



3 Cells oblong, ellipsoidal or cylindrical; sheath wanting; reproduction 



by cell division in one direction only Synechococcus 



4 Cells cylindrical or oblong-conical; sheaths thick, hyaline; reproduc- 



tion by cell division in one direction only Chroothece 



II. Plants associated in families or colonies, surrounded by a common 



gelatinous tegument. 



I Colonies without definite shape 



(i) Individual sheaths usually thick, remaining through many divi- 

 sions, sheath of original mother-cell surrounding entire colony 

 A Cells spherical 



a Cells enclosed in a vesicle-like, thick, colorless or colored 

 sheath, spherical (after division oblong), single or in colonies; 

 cell contents blue-green, or of various colors 



Gloeocapsa 

 b Cells surrounded by an elliptical membrane, forming colonies, 



arranged in short filaments Entophysalis 



c Cells surrounded by thick sheath, forming spherical colonial 

 masses; plant mass cushion-like, cartilaginous, incrusted with 

 lime at base, curled at periphery Chondrocystis 



B Cells elongate 

 a Cells cylindrical-oblong, surrounded by a thick, mucous sheath, 

 solitary or forming small colonies Gloeothece 



(2) Individual sheaths not distinct; colony surrounded by common 

 tegument formed of dissolved individual sheaths 

 A Cells spherical (or angular from mutual pressure); cell division 



in all directions Aphanocapsa 



B Cells oblong; cell division in one direction Aphanothece 



2 Colonies having a definite characteristic shape 

 (i) Colonies free-floating 



