Stonewort, Stonewort family Stonewort family genus of algae. Algae body purple-red or brown-red, flattened upright, clustered into pinnate branches, branchlets opposite or alternate, each branch end acute, generally 10-30 cm high. Uniaxial. Cortical cells with many root-like filaments between them. The tetrasporangium is formed from the terminal branches and divides in a cruciform pattern. The spermathecae and fruiting cells are also formed by the terminal branches, and the fruiting of the capsule protrudes on both sides, each with a small pore. The fruiting sporangium is clavate. It is a common species in the Yellow Sea, Bohai Sea and East China Sea. For food, but also the main raw material for the extraction of agar.