Batrachospermum, genus of freshwater red algae (family Batrachospermaceae) ranging in colour from violet to blue-green. The long, branched, threadlike filaments bear dense whorls of branchlets, resembling beads on a string. Spores are formed in clusters around the base of the carpogonium (female sex organ) after fertilization. The genus is widely distributed and can be found in cool streams and in pools in sphagnum bogs.