any protozoan of the plantlike flagellate order Heterochlorida. Heterochlorids have two flagella of unequal length and chromatophores with yellow to yellow-green pigments. Food reserves are stored as leucosin (a carbohydrate) and lipids. Some genera may be amoeboid during part of the life cycle; others may include a palmella stage, a condition in which the cells occur in a mucilaginous mass but continue to metabolize. Siliceous cyst walls are formed within the cytoplasm. Representative genera include Nephrochloris, Chloromeson, and Rhizochloris.