Xanthophyta is a phylum of kingdom Chromista that contains yellow-green algae. While there are more than 600 species of Xanthophyta, representative organisms are rare. Although Xantophytes are similar to the green algae in kingdom Plantae, the two divisions belong to completely different evolutionary lines. Like the other Chromists, Xanthophytes have chlorophyll c and two flagella (at some point in their life cycles), and they store energy in oils and polysaccharides. Xanthophytes are the only Chromists to lack the pigment fucoxanthin, which results in their yellow-green hue.
Species of Xanthophyta have several growth forms:
Xanthophytes live in both fresh and marine waters. Almost all xanthophytes reproduce exclusively asexually. Some filamentous forms reproduce by division, but most produce spores. Organisms of genus Botrydium possess isogamous sexual reproduction, while those of Vaucheria utilize oogamous sexual reproduction.
Xanthophyta is probably closely related to Phaeophyta, the phylum that contains kelps and brown algae. There are no known Xanthophytic fossils. The absence of fossils is probably due to the fact that the silaceous cysts in their cell walls have not been extensively studied.
- Green Plants by Peter Bell and Alan Hemsley