The nutrition of the plant-like flagellates is in some respects as puzzling as their morphologic characteristics. The chlorophyll-bearing Phytomonadida grow in the light in inorganic media, but they also grow in the dark with one or more amino acids as sources of N and C. The colorless Phytomonadida and the Euglenidae both show great species variation in their nutritive requirements, ranging all the way from those requiring only light and inorganic salts to those requiring peptone. The nutritive demands of many of the flagellates approach those of the more "animal-like" protozoa[long dash]an interesting evolutionary point.