No. IO.] FRESH-WATER ALG.E. 3 1 



ing radially. One, two, or four series of cells in each mem- 

 brane. 



FAMILY II. PROTOCOCCACE.E. 



The vegetative cells are green, strictly unicellular, and are 

 not provided with cilia. Propagation either sexual or asexual. 

 In the latter case the cells divide into many parts, the whole 

 assuming the form of a new colony. These are called auto- 

 spores and autocolonies. Division of vegetative cells lacking. 

 In some genera the cells are united into definite regular forms 

 called cccnobia, in others into a pseudocoenobium, which differs 

 from the true coenobium in that the cells are not all of the same 

 generation; other genera have the cells scattered or congre- 

 gated into irregular forms. 



Key to Sub -families. 



i. Cells elongated, frequently curved; solitary or in 



definite, loosely coherent colonies selenastre^: 



Cells angular, with a definite number of angles, two, 



four, six, eight, or more; cells solitary. . . tetraedre^e 

 Cells variable, united in a regular flat plate. . crucigenie.e 

 Cells globose or sub-globose 2 



2. Cells strictly globose, united in a spherical colony 



(coenobium) ccelastre.e 



Cells globose or sub-globose, not united in a spherical 

 coenobium 3 



3. Cells with two or more attenuated bristles. . .phythelie^: 

 Cells without bristles 4 



4. Cells generally retained within enlarged wall of 



mother-cell oocystidelf: 



Cells joined in colonies by persistent walls of mother- 

 cells, which sometimes become transformed into 

 connecting threads dictyosph^rie.e 



SUB-FAMILY I. DICTYOSPH^ERIEJE. 



Cells globose, ovoid, or ellipsoid, and associated to form 

 indefinite colonies. The cells are held in position, usually, by 

 the wall of the mother-cell, which in some genera breaks up 

 into connecting threads. Multiplication by simple vegetative 



