A simplified list of characteristics of ''algae'' includes the following:
phylum Chlorophyta: mostly freshwater, cell wall, chlorophylls a and b
phylum Euglenophyta: mostly freshwater, no cell wall, chlorophylls a and b
phylum Phaeophyta: mostly marine, cell wall, chlorophylls a and c
phylum Chrysophyta: marine and freshwater, cell wall, chlorophylls a and
phylum Pyrrhophyta: mostly marine, cell wall, chlorophylls a and
phylum Rhodophyta: mostly marine, chlorophylls a and phycobilin
From examination of this restricted set of data, and referring back to discussions of systematics and taxonomy, it is most likely that the most primitive algae