CHAPTER 4 



PHYTOFLAGELLATES 



In this section, "Phyto" will be de-emphasized in favor of 

 "flagellates". Any consideration in depth of such plant-like 

 features as chloroplasts and cell walls is beyond the scope of this 

 review and the competence of its author, and those aspects of 

 phytoflagellate structure that are particularly significant to a study 

 of the evolution of the higher algae and land plants must be largely 

 neglected. Rather, we are interested in the phytoflagellates as 

 spectacularly successful single-celled organisms whose ancestors 

 presumably existed for long ages before the first entirely animal- 

 like protozoan groups split off. 



One would like to be able to turn with some certainty to a 

 protistan group that includes the most primitive eucells in 

 existence today, and to ask what is the minimum structural equip- 

 ment with which such a cell can survive as an independent 

 organism. Unfortunately, not only is it improbable that any 

 contemporary organism exemplifies an ungarnished minimum 

 cell organization, but we do not know which of the several 

 distinct phytoprotistan lines is of most ancient origin, hence likely 

 to include the most nearly primitive types. 



If a monophyletic origin of all eucells is postulated, then 

 particular attention must be paid to the non-flagellated red algae, 

 which synthesize pigments more nearly like those of the blue- 

 green algae than do any other eucellular protista. Thus Dougherty 

 (1955) and Dougherty and Allen (1960) offer the unconventional 

 proposal that the first flagellates evolved from already eukaryotic 

 cells resembling simple red algae. 



An electron-microscope study has been reported by Brody and 

 Vatter (1959) of the unicellular red alga, Porphyridium cruentum. 

 This small cell is almost entirely occupied by a single chloroplast, 

 which contains the characteristic biliprotein pigment as well as 

 chlorophyll. The shape of the chloroplast is irregular, and the 



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