Myxophyceae 3 



A Cells having an indefinite arrangement, forming several layers 

 a Cells spherical or oblong; colony spherical or oblong, solid 



Microcystis 

 b Cells spherical; colonies of variable shape, at first solid, becom- 

 ing saccate and clathrate Clathrocystis 



c Cells pear-shaped or heart-shaped; colony spherical or ellip- 

 soid, solid Gomphosphaeria 

 B Cells having a definite arrangement, forming a single layer oi 

 cube 

 a Colonies spherical, hollov^r 



(a) Cells spherical, lying just within the periphery of the colony 



Coelosphaerium 



(b) Cells spherical or elongate; individual sheaths distinct 



Coelosphaeriopsis 

 b Colonies flat 

 ^ (a) Cells of some definite or symmetrical shape, quadrangular 

 or triangular, solitary or forming colonies 



Tetrapedium 

 (b) Cells spherical; colonies rectangular Merismopedium 

 c Colonies cubical, solid; cells spherical or elliptical 



Eucapsis 

 (2) Colonies adherent to substratum 



A Cells spherical or elongate, regularly arranged in radial rows; 

 colonies cushion-like, hard, leathery, verrucose 



Oncobyrsa 



B Cells spherical or oval, irregularly arranged in radial rows; col- 

 onies irregularly lobed, epiphytic Chlorogloea 



Gerius CHROOCOCCUS Naegeli. Gatt. Einz. Alg. 45. 1849. 



Plants either free-floating or forming a gelatinous or crust-like plant 

 mass in damp places, in fresh or salt water, or within the tissues of other 

 plants, occurring as spherical or angular cells, each surrounded by a more 

 or less definite sheath, solitary or united in twos, fours, eights, etc., but not 

 held together in definite colonies by a common gelatinous tegument; sheaths 

 thin or wide, homogeneous or lamellose, colorless or colored; cell contents 

 homogeneous or granular, usually of a blue-green color, sometimes violet, 

 olive-green, orange or yellowish; reproduction by successive division of the 

 cells alternately in three directions of space. 



I Sheaths hyaline, often lamellose; cell contents orange or yellowish. 



1 Cells less than 3 mic. in diameter C. rubrapunctus 



2 Cells more than 15 mic. in diameter 



(i) Plant mass yellowish green; cells 25-50 mic. in diameter •« 



C. macrococcus 



1 



; (2) Plant mass orange-colored; cells 19-34 ™'e. in diameter .. ,» 



C. turicensis ' 



