PHYTOMONADIDA 109 



Polytomella agilis Aragao (Fig. 37, h, c). With stigma and 

 numerous starch grains. Fresh water. 



Genus CoUodictyon Carter. Colorless. With pseudopodia. 

 Holozoic. 



CoUodictyon triciliatum Carter (Fig. 37, d). About 35 

 microns long. Fresh water. 



Genus Medusochloris Pascher. With four flagella; medusoid 

 in form and movement. Medusochloris phiale Pascher. 



Family 2 Chlamydomonadidae Biitschli 



Solitary; spheroid, oval, or ellipsoid in form; with a cellulose 

 membrane. Two or rarely four flagella. Chromatophores, 

 stigma, and pyrenoids are usually present. 



Genus Chlamydomonas Ehrenberg. Spherical, ovoid or 

 elongated; sometimes flattened. Two flagella. The membrane 

 is often thickened at the anterior end. Usually a large chromato- 

 phore, containing one or more pyrenoids. Stigma. A single 

 nucleus. Contractile vacuoles two in number at the anterior 

 end. Asexual reproduction and palmella formation are known. 

 Sexual reproduction is isogamy. Enormous number of species. 



Chlamydomonas monadina Stein (Fig. 37, e-g). Body about 

 20 microns long. Fresh water. Landacre noted that the or- 

 ganisms obstructed the sand filters used in connection with a 

 septic tank, together with the diatom Navicula. 



Chlamydomonas angulosa Dill (Fig. 37, h). Body about 15 

 to 20 microns. Fresh water. 



Genus Haematococcus Agardh ( = Sphaerella Sommerfeldt). 

 Spheroidal or ovoid with a gelatinous envelope. Chromato- 

 phores peripheral and reticulate, with two to eight scattered 

 pyrenoids. Several contractile vacuoles. Haematochrome is 

 frequently abundant both in motile and in encysted stages. 

 Asexual reproduction in motile form; sexual reproduction is 

 isogamy. 



Haematococcus lacustris (Girod) (Fig. 37, i). Body small, 

 8 to 30 microns long. Brick red; cysts are similarly colored. 

 The cause of "red snow" or "red rain." 



Genus Brachiomonas Bohlin. Lobate; with horn-like pro- 

 cesses, all directed posteriorly; no contractile vacuoles. Ill- 



