CHAPTER VIII 



ORDER 4 PHYTOMONADIDA BLOCHMANN 



THE PHYTOMONADIDA are small, more or less rounded, green 

 flagellates with a close resemblance to the algae. All of 

 them have a definite body form, and most of them are sur- 

 rounded by a cellulose membrane, which is thick in some and 

 thin in others. There is a definite opening in the membrane at 

 the anterior end, through which one or two (or seldom four 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 colorless forms are, however, saprozoic. 

 The metabolic products are usually amyloid substances. Some 

 Phytomonadida are stained red, owing to the presence of 

 haematochrome, or carotin. The contractile vacuoles may be 

 located in the anterior part or scattered throughout the body. 

 The nucleus is ordinarily centrally located. The nuclear 

 division seems to be mitotic, and chromosomes have 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. Isogamy 

 or anisogamy takes place with various gradations. Colony 

 formation also occurs, especially in the family Volvocidae. 

 Encystment and formation of the palmella stage are common 

 among many forms. 



The Phytomonadida are divided into five families: 



Without cellulose membrane; four or more flagella 



Family 1 Polyblepharidae 

 With cellulose membrane 

 Membrane a single piece 

 With chromatophores 



Two or four flagella; solitary Family 2 Chlamydomonadidae 



Two flagella; colonial Family 3 Volvocidae 



Without chromatophores Family 4 Polytomidae 



Membrane composed of two vahes Family 5 Phacotidae 



[ 107 1 



