Cephaleuros

Cephaleuros is a genus of thalloid green algae comprising approximately 14 species. Its common name is red rust. Cephaleuros species are parasitic algae which grow within vascular plants, typically within the subtropics or tropics.

== Description == Cephaleuros forms velvet-like spots up to 10 mm or more in diameter; these consists of a filamentous or pseudoparenchymatous, prostrate thallus and an erect system of filaments which branch from the prostrate thallus. The organism grows below the cuticle or epidermis of the host plant. Filaments branch dichotomously or pinnately, forming roughly circular thalli. Cells contain a single nucleus and an irregularly reticulate, parietal chloroplast with no pyrenoids. The cytoplasm often contains accumulations of carotenoid pigments, giving the thallus an orange-red color.