28 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



The order is a very large one, and contains an immense 

 variety of forms which can hardly admit of a general descrip- 

 tion. The order is divided into eight families, the following 

 six of which are known in the United States : 



Key to Families. 

 i. Unicellular, or of a definite number of ciliated motile 



Cells VOLVOCACEyE 



Cells not ciliated or motile 2 



2. Cells formed in flat plates or in a network 



HYDRODICTYACE.E 



Cells not in a plate or a network 3 



3. Unicellular and solitary; cell with differentiation of 



base and apex characiace^e 



Cells without differentiation of base and apex 4 



4. Unicellular and globular, or consisting of short, few- 



celled filaments (not truly filamentous) ; firm cell 

 walls ; no autospores pleurococcace^; 



Cells free or colonial, without copious gelatinous en- 

 velope, forming autospores protococcace^e 



Cells spherical and indefinite in number, embedded in 

 a copious gelatinous envelope palmellace^e 



FAMILY I. PALMELLACE^E. 



Unicellular Algae, free-floating or attached, single or in 

 families, with a conspicuous mucous envelope, which is with- 

 out definite form, and is either structureless or differentiated 

 into concentric envelopes. Cell contents at first homogeneous, 

 later granular, green or reddish. Multiplication by cell division 

 in two or three directions, and cells often grouped in twos or 

 fours. Asexual reproduction by biciliated zoogonidia, several 

 of which arise from an ordinary cell. Sexual reproduction has 

 been observed in some species. 



This family is divided into three sub-families, as follows : 



Key to Sub- families. 



Cells grouped in twos or fours within a lamellose 

 mucous investment glceocystide^e 



Cells grouped, in fours, irregularly disposed in a 

 mucus ; cells with a non-motile hair tetraspore^e 



