Padina boergesenii Allender & Kraft

Scientific Description

Habit and structure. Thalli light brown to tan, moderately ventrally calcified, 4–6 cm long and wide; blades broadly or narrowly lobed, short-stipitate from a bulbous fibrous holdfast. Creeping Vaughaniella stages reported by Allender & Kraft (1983, p. 88) but not confirmed from MELU herbarium holdings. Blades a mixture of 2 and 3 cell layers, 70–135 µmthick; cells of the ventral layer smaller than those of central and dorsal layers (longitudinal section), the dorsal cells 37–76 µmlong, 20–35 µmwide and 25–32 µmtall, the ventral cells 25–60 µmlong, 20–35 µmwide and 40–46 µmtall, or of almost the same dimensions as the dorsal cells; cells of central layer shorter than those of surface layers. Fronds usually consistently 3-layered at the base, 120–140 µmthick; surface cells commonly initiating uniseriate filaments that contribute to the stupose covering.

Reproduction. Sporangial sori non-indusiate, forming concentric bands between hair bands that alternate between opposite surfaces of the frond. Sporangia within sori maturing at very uneven rates, the mature sorus a mixture of developmental stages and closely bordered by single hair bands on the opposite and same side of the frond. Pre-meiotic sporangia 65–125 µm long and 75–85 µm in diameter, reaching 95–130 µm in diameter at division.

Distribution. This species has a scattered distribution across tropical, subtropical and warm-temperate regions. In Australia, it is know only from Lord Howe I.

[After Kraft, Algae of Australia: Marine Benthic Algae of Lord Howe Island and the Southern Great Barrier Reef, 2: Brown Algae:220–221 (2009)]