Electronic Flora of South Australia Species Fact Sheet

Phloiocaulon foecundum Sauvageau 1914: 457, figs 85–89.

Phylum Phaeophyta – Order Sphacelariales – Family Stypocaulaceae

Selected citations: Womersley 1967: 205.

Thallus (Fig. 60C) dark brown. 5–15 (–25) cm long, with one to a few axes from a small discoid base 0.5- l(–2) mm across; axes and laterals smooth, denuded in their lower parts, bearing above alternate, dense, fasciculate tufts along the main laterals; epilithic. Branching of several orders, radial to subdistichous near the apices with laterals every 2–4 (–10) segments (Fig. 62A), with most laterals determinate and tapering to a point over their upper one third; laterals with a single, large, inner cell (later subdivided) and a single-layered cortex of elongate cells which divide transversely to give a row of 4–6 (usually 4) cells per segment; loose descending rhizoids absent, but appressed rhizoidal filaments developing at base of lateral tufts; phaeophycean hairs in clusters in axils of laterals near apices. AXCS (Fig. 62B) 200–400 (–500) µm in diameter, smooth surfaced, with a secondary cortex which on older axes develops an outer cortex of radial filaments of small cells (Fig. 62B); uncorticated laterals (Fig. 62A) 80–120 in diameter with segments L/B 0.5–0.8 for most of their length, shorter near the tapering tips.

Reproduction: Unilocular sporangia (Fig. 62C) in dense spikes of overlapping ramuli hiding the reproductive organs, with the sporangia both in axils of laterals (more or less subtended by short ramuli) and directly on the axis between the laterals, each with a short pedicel 2–3 segments long, subspherical to ovoid, 100–160 (–180) µm in diameter. Sexual plants (Fig. 62D) with small, mixed, clusters of macro- and microgametangia borne similarly to the sporangia on axes and in axils of laterals; macrogametangia subspherical to ovoid, 120–140 µm in diameter, with loculi 4–6 µm across; microgametangia subspherical to slightly lobed, (120–) 140–160 µm in diameter, with loculi 2–4 µm across.

Type from Port Fairy, Vic. (Harvey, 1854); in TCD.

Selected specimens: Robe, S. Aust., 3–5 m deep under ledges (Mitchell, March 1959; ADU, A22883, sexual). Port MacDonnell, S. Aust., reef pools (Womersley, 25.i.1967; ADU, A31691, sexual). Lady Julia Percy I., Vic., 8–13 m deep (Shepherd, 5.i.1968; ADU, A32326, sexual). Port Fairy, Vic., drift (Muir, Jan. 1950; ADU, A15785, sporangial). Snowy R. mouth, Vic. (Mueller; MEL, 15770). Ulverstone, Tas., drift (Gordon, 18.i.1966; ADU, A30102). Blow Hole, Eaglehawk Neck, Tas., drift (Levring, 1.xi.1948; ADU, A56215). Port Arthur, Tas. (Lucas, Feb. 1927; HO, 68949).


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

Distribution: From Robe, S. Aust. to the Snowy R. mouth, Vic., and around Tasmania.

Taxonomic notes: P. foecundum appears to be restricted to heavily shaded pools or under ledges, or deeper water, on the south-east coasts of Australia. It differs from P. spectabile in having dense spikes of numerous overlapping laterals which hide the reproductive organs from view; the reproductive organs are borne in the axils and on the axes of the spikes, between the laterals.

References:

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 60C, 62 A–D.

Figure 60 image

Figure 60   enlarge

Fig. 60. A. Halopteris paniculata (ADU, A13396). B. Phloiocaulon spectabile (ADU, A35030). C. Phloiocaulon foecundum (ADU, A22883). D. Cladostephus spongiosus (ADU. A55543).

Figure 62 image

Figure 62   enlarge

Fig. 62. A–D. Phloiocaulon foecundum (A,B,D, ADU, A32326; C, ADU, A 15785). A. Upper branch system with indeterminate and determinate laterals and axillary phaeophycean hairs. B. Transverse section of old axis showing primary and secondary cortex. C. Longitudinal view of axis of sporangial plant. D. Axis of sexual plant with macro- and microgametangia. E–G. Cladostephus spongiosus (ADU, A55543). E. Longitudinal section of an axis showing upwardly curved determinate laterals and short simple, ecorticate laterals. F,G. Fertile laterals with plurilocular gametangia.


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