Key to the Families 



1. Cells solitary, naked, i.e., inclosed only by a membrane; cell wall lack- 

 ing _. __ POLYBLEPHARIDACEAE 



1. Cells possessing a definite wall and sometimes a mucilaginous sheath; 

 solitary or united in colonies __- 2 



2. Cells solitary 3 



2. Cells united in colonies 5 



3. Wall bivalved, the cells compressed and the halves of the wall adjoined 

 along their lateral margins __,_ "phacotaceae 



3. Wall not bivalved; cells not flattened 4 



4. Cells with protoplasts located at some distance within the cell wall and 

 connected to it by radiating cytoplasmic 



strands haematococcaceae (in part) 



4. Cells without radiating cytoplasmic strands chlamydomonadaceae 



5. Cells with many radiating cytoplasmic processes connecting the proto- 

 plast with the cell wall haematococcaceae (in part) 



5. Cells without such radiating protoplasmic processes.- .— .— 6 



6. Cells united to form flat or globular colonies, evenly dispersed, although 

 sometimes closely arranged within colonial mucilage volvocaceae 



6. Cells compactly united in tiers of 4 with their anterior ends all directed 

 the same way; gelatinous sheath lacking .._ _ spondylomoraceae 



FAMILY POLYBLEPHARIDACEAE 



The chief characteristic of this family of unicellular individuals 

 is the lack of a cellulose wall, the protoplast being inclosed by a 

 membrane only. The cells have 2-4-8 anterior flagella of equal 

 length, with contractile vacuoles sometimes present at their bases. 

 A red pigment-spot is normally present. The chloroplast varies in 

 form among the different members; usually it is a parietal cup con- 

 taining a pyrenoid. Of the 7 genera reported from North America 

 only 1 is known from this region at present. 



PYRAMIMONAS Schmarda 1850, p. 9 



Cells hemispherical or obpyriform, broadest at the anterior end, 

 which is depressed and 4-lobed; 4 flagella attached in the apical 

 depression, with 2 contractile vacuoles below their point of attach- 

 ment. Chloroplast a parietal cup with a pyrenoid in the posterior 

 portion. 



Pyramimonas tetrarhynchus Schmarda 1850, p. 9 

 PI. 1, Figs. 1, 2 

 Cells pyriform with the anterior end conspicuously 4-lobed; fla- 

 gella attached close together in the apical depression. Chloroplast a 

 parietal cup with 4 lobes. Cell 12-18;u in diameter, 20-28;a long. 

 Wis. 



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