Chapter 10 

 Order 3 Phytomonadina Blochmann 



THE phytomonads are small, more or less rounded, green flagel- 

 lates, with a close resemblance to the algae. They show a definite 

 body form, and most of them possess a cellulose membrane, which 

 is thick in some and thin in others. There is a distinct opening in the 

 membrane at the anterior end, through which 1-2 (or seldom 4 or 

 more) flagella protrude. The majority possess numerous grass-green 

 chromatophores, each of which contains one or more pyrenoids. The 

 method of nutrition is mostly holophytic or mixotrophic; some color- 

 less forms are, however, saprozoic. The metabolic products are 

 usually starch and oils. Some phytomonads are stained red, owing 

 to the presence of haematochrome. The contractile vacuoles may be 

 located in the anterior part or scattered throughout the body. The 

 nucleus is ordinarily centrally located, and its division seems to be 

 mitotic, chromosomes having been definitely noted in several species. 



Asexual reproduction is by longitudinal fission, and the daughter 

 individuals remain within the parent membrane for some time. 

 Sexual reproduction seems to occur widely. Colony formation also 

 occurs, especially in the family Volvocidae. Encystment and forma- 

 tion of the palmella stage are common among many forms. The 

 phytomonads have a much wider distribution in fresh than in salt 

 water. 

 Solitary 



Membrane a single piece; rarely indistinct 



2 flagella Family 1 Chlamydomonadidae 



3 flagella Family 2 Trichlorididae (p. 222) 



4 flagella Family 3 Carteriidae (p. 222) 



5 flagella. Family 4 Chlorasteridae (p. 224) 



6 or more flagella Family 5 Polyblepharididae (p. 224) 



Membrane bivalve Family 6 Phacotidae (p. 225) 



Colonial, of 4 or more individuals; 2 (1 or 4) flagella 



Family 7 Volvocidae (p. 225) 



Family 1 Chlamydomonadidae Butschli 



Solitary; spheroid, oval, or ellipsoid; with a cellulose membrane; 

 2 flagella; chromatophores, stigma, and pyrenoids usually present. 



Genus Chlamydomonas Ehrenberg. Spherical, ovoid or elongated; 

 sometimes flattened; 2 flagella; membrane often thickened at an- 

 terior end; a large chromatophore, containing one or more pyrenoids; 

 stigma; a single nucleus; 2 contractile vacuoles anterior; asexual 



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