Electronic Flora of South Australia Species Fact Sheet

Distromium multifidum Womersley 1967: 220, fig. 4.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae

Reproduction: Sori (Fig. 83A,B) small, with 4–12 sporangia, on the concave (upper) side of branch ends, with a membranous indusium; sporangia (Fig. 83B,C) developed directly from thallus cells (without a stalk cell), external to the thallus, subspherical to ovoid, (120)150–200 (–240) gm in diameter, tetrahedrally divided. Oogonia unknown. Antheridia (Fig. 83D) present on sporangial plants (ADU, A23956); sori on concave branch ends, 400–600 µm long and 200–300 µm across; antheridia 60–90 µm long, 20–40 µm in diameter.

Type from Victor Harbor, S. Aust., drift ( Womersley, 19.ix.1965); in ADU, A29525.

Selected specimens: Hopetoun, W. Aust., 3–4 m deep on old jetty piles (Kraft 6994 & Ricker, 16. viii.1979; ADU, A50723). Elliston Bay, S. Aust., 10–12 m deep (Shepherd, 23.x.1969; ADU, A34940). Pearson I., S. Aust., 28 m deep (Shepherd, 9.i.1969; ADU, A34002). Barker Rocks, Yorke Pen., S. Aust., drift (Womersley, 24.ix.1967; ADU, A31960). Port Willunga, S. Aust., drift (Womersley, 25.x.1959; ADU, A23956-sporangial with antheridia). D'Estrees Bay, Kangaroo I., S. Aust., drift ( Womersley, 23.viii.1963; ADU, A26802). Portland, Vic., 20 m deep, 5 km off Surry R. mouth (Watson, 28.xi.1981; ADU, A52808). Red Rocks, Phillip I., Vic., drift ( Womersley, 25.x.1986; ADU, A57260). East Cove, Deal I., Bass Str., Tas., 15 m deep (Shepherd & Lewis, 7.v.1974; ADU, A45081).


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

Distribution: From Hopetoun, W. Aust. to Phillip I., Vic. and Deal I., Bass Strait, in depths of 3 to 28 m.

Taxonomic notes: 7'hallus (Figs 80C, 83A) medium to dark brown, erect, usually 3–8 cm long and 4–10 cm in spread, much divided into linear, subdichotomous branches, usually slightly twisted above, attached by a matted rhizoidal holdfast 0.2–1.0 cm across and 0.2–0.5 cm long, with one to several axes with descending rhizoids from the lower to mid branches; epilithic. Growth from an irregularly rounded row of many apical cells (Fig. 83B) in actively growing branches. Fronds (Fig. 83A) with irregularly linear branches 400–1000 µm broad, broadening slightly to below the apices which are 1–1.5 mm across. Structure (Fig. 83C,D) two cells and 50–85 µm thick throughout, cells in surface view 20–35 (–45) um across, L/B (2–) 3–5. Rhizoids developing centrally on both sides of mid thallus segments, spreading laterally, branched with denser terminal cells when young. Phaeophycean hairs in small, inconspicuous, scattered tufts (Fig. 83B) or absent, on the upper side, 14–18 µm in diameter, with a basal meristem.

Distromium multifidum is readily recognized by its much branched, distromatic thallus, with sporangia in concave branch ends. The single record of antheridia applies to otherwise sporangial plants, similar to the situation in Taonia lennebackeriae (Mathieson 1966).

References:

MATHIESON, A.C. (1966). Morphological studies on the marine brown alga Taonia lennebackerae Farlow ex J. Agardh. I. Sporophytes, abnormal gametophytes and vegetative reproduction. Nova Hedwigia 12, 65–79, Plates 11–14.

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

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 80C, 83 A–D.

Figure 80 image

Figure 80   enlarge

Fig. 80. A. Chlanidophora microphylla (ADU, A54821). B. Distromium flabellatum (ADU, A19784, holotype). C. Distromium multilidum (ADU, A29525, holotype).

Figure 83 image

Figure 83   enlarge

Fig. 83. A–D. Distromium multifidum (A–C, ADU, A29525, holotype; D, ADU, A23956). A. Branches with sori of sporangia. B. Branch end with marginal apical cells and sporangia. C. Transverse section of thallus with sporangia. D. Longitudinal section of thallus with a sorus of antheridia. E–H. Spatoglossum australasicum (ADU, A34905). E. Branch apex showing small groups of apical cells and scattered phaeophycean hair tufts. F. Meristem at apex of a branch, showing apical cells and segmentation. G. Longitudinal section from apical cell (right) to mature thallus (left) showing segmentation. H. Transverse section of mature thallus with a sunken phaeophycean hair tuft.


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