Spermolepis hawaiiensis, a member of the parsley family (Apiaceae), is a slender annual herb with few branches, which grows to a height of 5 to 20 cm (2 to 8 in). Its leaves, dissected into narrow, lance-shaped divisions, are oblong to somewhat oval in outline and grow on stalks about 2.5 cm (1.0 in) long. Flowers are arranged in a loose, compound umbrella-shaped inflorescence arising from the stem, opposite the leaves. Each cluster consists of two to six flowers, with each flower on a stalk between 2.0 and 6.0 mm (0.08 and 0.2 in) long. The calyx is lacking in this species, but one to five bracts grow below the clusters of flowers. The fruits are oval and laterally compressed and constricted at the line where the two halves of the fruit meet. The fruits are 4.0 mm (0.2 in) long and 3.0 mm (0.1 in) wide, covered with curved bristles, and contain seeds that are marked with longitudinal grooves beneath oil tubes that are characteristic of the parsley family. Spermolepis hawaiiensis is the only member of the genus native to the Hawaiian Islands.