FAMILY CHLAMYDOMONADACEAE 



The unicellular organisms which compose this family have a 

 smooth cellulose membrane in 1 piece. There are 2 or 4 flagella, 

 equal in length, and 2-4 contractile vacuoles at the anterior end of 

 the cell. In most forms the chloroplast is cup-shaped and contains 1 

 to several pyrenoids (posterior or scattered) and a red pigment-spot 

 laterally placed, usually anterior. 



Members of this family should be compared with those of the 

 Phacotaceae in which the cell wall is in 2 valve-like pieces that 

 adjoin along the lateral margins; and with the Haematococcaceae, 

 in which there are radiating protoplasmic processes extending from 

 the cytoplasm to the cell wall. 



There are 10 genera of this family reported from the United States, 

 but only 2 of these have appeared in our collections. 



Key to the Genera 



Cells with 4 flagella Carteria 



Cells with 2 flagella Chlamydomonas 



CHLAMYDOMONAS Ehrenberg 1835, p. 288 



Cells ovoid, ellipsoid, or spherical, sometimes with 1 or 2 apical 

 papillae, from which the 2 flagella arise; often with a narrow or wide 

 mucilaginous sheath. Chloroplast a dense, padded body occupying 

 the entire cell, or a thin parietal cup (in a few species H-shaped or 

 stellate); pyrenoids 1 to many, basal or bilateral and scattered; 

 pigment-spot lateral and anterior, rarely median; 2-4 apical contrac- 

 tile vacuoles usually discernible. 



Species of this genus have the habit of coming to rest, losing their 

 flagella, and entering upon a quiescent phase. Vegetative cell divi- 

 sion continues, ordinarily accompanied by the secretion of mucilage, 

 so that amorphous gelatinous masses are formed which contain 

 many nonmotile cells. This is known as the palmella stage. Unicellu- 

 lar or colonial algae in which the cells are ovate or globose and 

 which have cup-shaped chloroplasts (e.g., Gloeocystis) should be 

 compared, in making identifications, with this palmelloid expression 

 of Chlamydomonas. 



Key to the Species 



1. Cells inhabiting the empty loricas of Dinobryon C Dinobryonii 



1. Cells not inhabiting the loricas of Dinobryon 2 



2. Cells with axial pyrenoids, basal or median 3 



2. Cells with 1 or more pyrenoids, lateral or scattered 7 



3. Cells without an apical papilla C. globosa 



3. Cells with 1 or more apical papillae 4 



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