Electronic Flora of South Australia Species Fact Sheet
Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae
Thallus (Fig. 74B,C) medium brown throughout, lightly calcified on the upper surface, not or only slightly on the lower surface, 4–8 cm long and 4–10 cm in spread, when young flabellate and usually becoming shallowly to occasionally deeply divided, with acute to rounded axils, attached by a rhizoidal holdfast 2–10 mm long and 2–6 mm across; epilithic. Structure (Fig. 75L,M) of two layers of cells of similar size throughout or with the upper side cells shorter, 70–100 µm thick near the apices and 100–140 µm thick below. Cells in surface view of upper side 20–30 µm broad, L/B 1.5–3 (–4), on lower surface 25–35 µm broad, L/B 1–1.5 (–2). Hairs (Fig. 75K) in alternating concentric lines on both sides of the thallus, 2–4 mm apart on each side, (12–) 14–24 µm in diameter.
Reproduction: Sporangia (Fig. 75K,M) in concentric, continuous or broken, sori on the upper side of the thallus, above each of the hair lines but with alternate fertile and sterile zones when the hair lines on both sides are viewed together; indusium slight; sporangia ovoid and broad based, 80–100 (–120) µm long and 50–80 (–100) µm in diameter. Sexual plants unknown.
Type from Mudurup Reef, Cottesloe, W. Aust. (Koh, 17.iii.1969; holotype in UWA, A962).
Selected specimens: Port Denison, W. Aust. on outer reef (Borowitzka, April 1979; ADU, A52417). Natural Jetty Reef, Rottnest I., W. Aust., upper sublittoral ( Woelkerling, 10.xi.1968; ADU, A33329). Nancy Cove, Rottnest I., W. Aust., 4 m deep (Walker, 16.v.1986; ADU, A57113. Eucla, S. Aust., drift (Womersley, 2.ii.1954; ADU, A19325). Pearson I., S. Aust., 20–25 µm deep (Shepherd, 8.i.1969; ADU, A33865-sterile).
Distribution: From Port Denison, W. Aust., to Pearson I., S. Aust.
Taxonomic notes: P. elegans is similar in form and thallus thickness to P. sanctae-crucis, but differs in that in transverse section both cells are of similar height and remain only 2 cells thick, and the sporangial sori are on the upper side only, with a more prominent indusium than in P. sanctae-crucis.
Other bistratose species with an indusium over the sporangial sori are P. minor Yamada 1925, which has sori on the lower side and is close to, possibly not distinct from, P. sanctae-crucis; P. haitiensis Thivy in Taylor (1960, p. 235) which may also be the latter species; P. perindusiata Thivy in Taylor (1960, p.235) for which the side of the thallus bearing sporangia is not stated but the lower cell layer is 0.33 to 0.5 as deep as the upper; and P. thivyae Doty & Newhouse 1966 where the sori occur on both surfaces and the upper cells are taller than those of the lower layer (in basal thallus, lower layer is 40–50 µm thick and upper 120–150 µm thick).
DOTY, M.S. & NEWHOUSE, J. (1966). Three new species of the Phaeophyta from Hawaii. Occas. Pap. Bernice P. Bishop Mus. 23, 139–146.
TAYLOR, W.R. (1960). Marine algae of the eastern tropical and subtropical coasts of the Americas. (Univ. Mich. Press: Ann Arbor.)
YAMADA, Y. (1925). Studien fiber die Meeresalgen von der Inseln Formosa, 2. Phaeophyceae. Bot. Mag. Tokyo 39, 239–254.
The Marine Benthic Flora of Southern Australia Part II complete list of references.
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
Illustrations in Womersley Part II, 1997: FIGS 74B,C, 75 K–M.
Figure 74 enlarge
Fig. 74. A. Padina sanctae-crucis (ADU, A13892). B. Padina elegans (UWA, A962, holotype). C. Padina elegans (ADU, A19325).
Figure 75 enlarge
Fig. 75. A–C. Padina gymnospora (ADU, A50599). A. Longitudinal section of thallus, showing inrolled apex, hair lines and sporangial sori. B. Longitudinal section with a sporangial sorus. C. Transverse section of older thallus. D–G. Padina fraseri (ADU, A51069). D. Longitudinal section of thallus showing inrolled apex, hair lines and sporangial sori. E. Transverse section of young thallus. F. Transverse section of older thallus with rhizoids. G. Longitudinal section of thallus with a sorus of sporangia. H–J. Padina sanctae-crucis (ADU, A13892). H. Longitudinal section of thallus showing inrolled apex, hair lines and sporangial sori. I. Longitudinal section of thallus with a sorus of sporangia. J. Transverse section of older thallus. K–M. Padina elegans (ADU, A33329). K. Longitudinal section of thallus showing inrolled apex, hair lines and sporangial sori. L. Transverse section of young thallus. M. Longitudinal section of thallus with a sorus of sporangia.
State Herbarium of South Australia