HOW TO KNOW THE FRESH-WATER ALGAE 



77a Cells ellipsoid or somewhat fusiform; chloroplast 1 or 2 longitudinal 

 lateral bands. Fig. 63 CHLORANGIUM 



Figure 63 



Fig. 63. Chlorangium stentorinum (Ehr.) Stein. 



This organism becomes attached, anterior end 

 down, to small crustaceans and other microscopic 

 animals by means ot a gelatinous stalk. Although 

 a swimming cell, the tlagella are thrown off and the 

 organism continues to divide, the stalk becoming 

 branched as new individuals arise so that a colony 

 results. Some small animals such as Cyclops may 

 go swimming about with veritable plumes of the 

 green cells growing on their antennae. The cells 

 have 2 elongate, parietal chloroplasts. Compare 

 Chlorangium with Colacium (Fig. 64). 



77b Cells ovate to oblong or ovoid; chloroplasts numerous ovoid discs. 

 Fig. 64 COLACIUM 



Fig. 64 a, Colacium arbuscula Stein; b, 

 C. vesiculosum Ehr. 



Microscopic animals, especially crusta- 

 ceans, may appear green because of the 

 large numbers of Colacium individuals at- 

 tached to them, either singly or in plume- 

 like clusters. Like Chlorangium (Tig. 63) 

 this organism is a motile green cell which, 

 however, has numerous Eugiena-like chlo- 

 roplasts (Fig. 8) and a conspicuous red 

 b pigment-spot. The rather specific associ- 

 ation of the algal cells with the animal 

 host incites speculation as to how this 

 relationship is maintained. 



Figure 64 



78a (76) Cells ellipsoid or spindle-shaped, attached end to end form- 

 ing loose branching chains. Fig. 65 DACTYLOCOCCUS 



Sfc*5^ 



Fig. 65. Dactylococcus intusionum Naeg. (Re- 

 drawn from Smith.) 



This anomalous genus is known from soil 

 collections of aigae. The characteristic chain- 

 like arrangement of the cells develops as the 

 cells are cultivated whereas they probably 

 are solitary in nature. 



Figure 65 



78b Cells not arranged in branching chains 



79 



52 



