Ohwi 1985 Flora of Japan

Red List information (2000): It grows on sandy sea bottom at a depth of 6-12 meters. Its leaves are 10-15 mm wide and have nine veins. Long branches grow from the rhizome and stand upright in the water. Flowers only appear on the lower part of the branches, while only leaves grow on the upper part. The vertical stripes on the seed coat are unclear.

 

In the IUCN red list, it is referred to as "DD." It has gone extinct in one of the 12 natural habitats. In other natural habitats, except for one location, only small populations are observed. Due to its limited natural habitat and the impact of development, it is classified as "VU" (vulnerable).