Padina japonica

Padina japonica has a flat blade rolled into a circle. The upper surface is whitish while the underside is brown. It is similar to Padina australis but rather smaller and the blade is usually unsplit.^[2] Another very similar species is Padina sanctae-crucis; the underside of the latter is more highly calcified, the oogonia and the tetrasporangia are large and globular rather than small and oblong, and there is a single row of tetrasporangial sori rather than the multiple irregular rows of P. japonica.^[3]