Padina spp.
Phaeophyta, Dictyotaceae
Authority: Adanson
Hawaiian name: none
Characteristic feature: Flat blade with inrolled margins, brown in color with white calcification.
Description: Plants fan-shaped, becoming split with age, usually growing in small groups or communities, attached by conical holdfast of rhizoids, usually erect; growth from marginal meristem lining leading edge of blade, with apical cells enclosed in inrolled (involute) margin at terminal portions of frond; when blade unrolls, portion being exposed becoming inner side, opposite side (or back of roll) becoming outer side; frequently calcified on one or both surfaces. Below inrolled margin, rows of hairs or their scars forming arching lines from one lateral margin to other, floowed proximally by line of sporangia or another hair line preceding sporangial row; in some species, hair lines close to sporangial line, in others distant. Hair and sporangial lines may alternate on either side of frond (inner and outer sides), thus providing several different arrangements for different species. Blades usually two to several cells thick, not conspicuously differentiated into medulla and cortex.
Habitat: Specimens from upper intertidal pools to 3 m deep, on intertidal benches and mid- to low intertidal areas at the back of reef flats.
Hawaiian distribution: All main Hawaiian Islands, including the Northwestern Hawaiian Islands.
Other: Identification of the seven Hawaiian species is by the number of cell layers, arrangement of sporangia, spacing of sporangial bands relative to hair lines or bands, location of sporangial bands, and indusia covering the sporangia.