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Leathesia intermedia Chapman 1961: 20, fig. 4.

Phylum Phaeophyta – Order Chordariales – Family Leathesiaceae

Selected citations: Lindauer et al. 1961: 221, fig. 45. Womersley 1967: 230, fig. 6.

Thallus (Fig. 27D) brown, 2–25 mm across, usually globose and solid, sometimes lobed, mucoid, epiphytic. Basal layer of radiating filaments of small cells, 4–6 µm in diameter, with some rhizoidal filaments of similar cells. Medulla extensive, 1–20 mm high, of subdichotomous filaments of fairly compact, ovoid to pyriform cells 50–120 µm in diameter and L/B 1–3, smaller above, with occasional lateral anastomoses. Determinate cortical filaments (Fig. 29G,H) borne on uppermost medullary cells, arising singly or in small groups from a subtending cell, simple or once branched, forming a dense, compact, stratum 80–120 µm and 4–8 (–10) cells high; cells cylindrical, (4–) 5–6 µm in diameter and L/B 1.5–2, with a terminal globose to slightly pyriform or broadly obovate cell (15–) 20–40 µm in diameter when mature. Phaeoplasts (Fig. 29H) several per cell, peripheral or mainly in the upper end of terminal cells, discoid to laminate, pyrenoids unclear if present. Phaeophycean hairs borne on basal cell to the cortical filaments, scattered, 6–10 µm in diameter.

Reproduction: Plurilocular sporangia (Fig. 29G) borne in corymbose, pedicellate, clusters from uppermost medullary cells, uniseriate or with occasionally biseriate locules, filiform, (20–) 30–40 µ and 8–15 locules long, 4–6 µm in diameter. Unilocular sporangia (Fig. 291) on the same thallus, borne on the subtending cell of the cortical filaments, ovoid to clavate, 40–55 µm long and 20–25 (–30) µm in diameter.

Type from Stewart I., New Zealand; in Herb. Lindauer, CHR.

Selected specimens: Robe, S. Aust., on Caulerpa simpliciuscula, upper sublittoral in bay (Skinner, 14.xi.1978; ADU, A50216). Nora Creina, S. Aust., on Caulocystis cephalornithos, drift ( Womersley, 19.xii.1970; ADU, A37814). Apollo Bay, Vic. on Zonaria angustata (Parsons, 23.i.1967; ADU, A31410). Queenscliff, Vic. on Halopteris, low eulittoral (Skinner, 4.i.1978; ADU, A49063). Rocky Cape, N. Tas., on Polysiphonia decipiens, drift (Gordon, 18.i.1966; ADU, A29943). Safety Cove, Port Arthur, Tas., on Gelidium australe in deep pools (Skinner, 21.ii.1978; ADU, A49179-"Marine Algae of southern Australia" No. 195).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Taranaki and Stewart I., New Zealand.

In southern Australia, from Robe, S. Aust. to Port Phillip, Vic., and around Tasmania, epiphytic on a wide variety of larger algae (e.g. Caulerpa, Halopteris, Dictyopteris, Sargassum, Gelidium, and Polysiphonia).

Taxonomic notes: Leathesia intermedia is not uncommon on south-east Australian coasts, and agrees well with New Zealand material. It is distinguished by the longer determinate cortical filaments with the much larger terminal cell than in L. difformis. L. intermedia is closest to the Japanese L. sphaerocephala Yamada and L. pulvinata Takamatsu (Inagaki 1958, pp. 115,117) but differs in the size and shape of the terminal cells of the cortical filaments.


CHAPMAN, V.J. (1961). New entities and combinations in the Phaeophyceae of New Zealand. Bull. Res. Counc. Israel 10D, 15–28.

INAGAKI, K. (1958). A systematic study of the order Chordariales from Japan and its vicinity. Sci. Pap. Inst. Algol. Res. Hokkaido Univ. 4, 87–197, Plates I-XI.

LINDAUER, V.W., CHAPMAN, V.J. & AIKEN, M. (1961). The marine algae of New Zealand. II. Phaeophyceae. Nova Hedwigia 3, 129–350, Plates 57–97.

WOMERSLEY, H.B.S. (1967). A critical survey of the marine algae of southern Australia. II. Phaeophyta. Aust. J. Bot. 15, 189–270.

The Marine Benthic Flora of Southern Australia Part II complete list of references.

Author: H.B.S. Womersley & S. Skinner

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

Illustrations in Womersley Part II, 1997: FIGS 27D, 29 G–I.

Figure 27 image

Figure 27   enlarge

Fig. 27. A. Elachista australis on Xiphophora chondrophylla (ADU, A34809). B. Corynophlaea cystophorae on Cystophora tnoniliformis (ADU, A46767). C. Leathesia difformis (ADU, A44619). D. Leathesia intermedia on Gelidium australe (ADU, A49179).

Figure 29 image

Figure 29   enlarge

Fig. 29. A–C. Petrospongium rugosum (A, ADU, A49080; B,C, ADU, A50231). A. Habit. B. Thallus section showing medulla (with hyphae), cortex of branched filaments, phaeophycean hairs and unilocular sporangia. C. Cells of a determinate cortical filament with phaeoplasts and physodes. D–F. Leathesia difformis (D,E, ADU, A44619; F, ADU, A48248). D. Thallus section showing large, anastomosing medullary cells, determinate cortical filaments, plurilocular sporangia and phaeophycean hairs. E. Determinate cortical filament with phaeoplasts. F. Upper medulla and cortex with unilocular sporangia and a phaeophycean hair. G–I. Leathesia intermedia (G,H, ADU, A49179; I, ADU, A29943). G. Thallus section showing large medullary cells, determinate cortical filaments with large terminal cells, plurilocular sporangia and phaeophycean hairs. H. Determinate cortical filament with phaeoplasts and physodes. I. Outer medulla and cortex with unilocular sporangia and a phaeophycean hair.

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