Charophyta are freshwater plants and generally grow anchored to the substratum by rhizoids with a shoot extending upward. The shoot then divides and forms nodes from which a whorl of side filaments projects. Charophyta reproductive structures develop at these nodes and are, along with the biflagellate sperm produced in the male gametangium, quite similar to those of mosses. These similarities have led some scientists to identify the charophytes as ancestors of the mosses. Their green color comes from chlorphylls a and b.