Yellow-green algae

Yellow-green algae or xanthophytes are an important group of heterokont algae. Most live in freshwater, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamentous forms. Unlike other heterokonts, their chloroplasts do not contain fucoxanthin, which accounts for their lighter colour. They appear to be the closest relatives of the brown algae.

Orders
The Xanthophyceae have been divided into the following four orders in some classification systems:


 * Order Botrydiales
 * Order Mischococcales
 * Order Tribonematales Pascher
 * Order Vaucheriales Nägeli ex Bohlin

Recent ultrastructural and molecular phylogenetic DNA (nuclear and plastid) research shows that the Mischococcales might be paraphyletic, and the Tribonematales and Botrydiales polyphyletic, and suggests two orders at most be used until the relationships within the division are sorted :


 * Order Tribonematales
 * Order Vaucheriales