Electronic Flora of South Australia Family Fact Sheet

ORDER SPOROCHNALES Sauvageau

Phylum Phaeophyta

Thallus (sporophyte) erect, usually 15–50 cm long, moderately to much branched radially with prominent main axes, or with clusters of laterals, branches terete or compressed (Carpomitra), normally with well developed, dense terminal or lateral clusters of simple assimilatory hairs, 3–15 mm long, to each branch, attached by a discoid to massive holdfast. Growth from a meristem at the apex of each branch, producing filaments of elongate cells downwards, with each terminal hair having a well defined meristem a few cells above its base. Structure haplostichous, with the filaments adhering closely to form a pseudoparenchymatous medulla, the outer cells of which divide periclinally to form a small-celled cortex 1–2 cells thick, surface smooth or with short, papillate, surface filaments or with long, stout, basally meristematic assimilatory filaments; cells of cortex and assimilatory hairs with numerous discoid phaeoplasts, without pyrenoids, and with physodes. Phaeophycean hairs absent.

Reproduction: The sporophyte by unilocular meiosporangia, sessile on cortical cells or developed laterally partway up densely clustered paraphyses which form sori on the branches, adjacent to or below the apices. Gametophytes (Caram 1965; Müller et al. 1985) monoecious or dioecious, oogamous.

Life history diplohaplontic and heteromorphic, with a conspicuous sporophyte and microscopic, filamentous, gametophyte.

Taxonomic notes: The Sporochnales contain a single family, Sporochnaceae, with the characters of the order. Clayton (1981a, p.117) placed the Sporochnales as a family of the Desmarestiales, and the two orders show similarities in life history and gametophytes. The habit, apical hair tufts and development, and structure of the thalli are, however, sufficiently distinct to place them as two orders, though perhaps distantly related.

The Sporochnaceae contain 10 genera, 8 of which (see below) occur in southern Australia (the distributional centre of the group), one (Tomaculopsis Cribb 1960, p. 18) in Queensland, and one (Perisporochnus Chapman 1954, p. 201) at the Three Kings Is, New Zealand.

References:

CARAM, B. (1965). Recherches sur la reproduction et le cycle sexué de quelques Phéophycées. Vie et Milieu 16, 21–222.

CHAPMAN, V.J. (1954). Algae of the Three Kings Islands, New Zealand. Rec. Auck. Inst. Mus. 4, 199–204, Plate 38.

CLAYTON, M.N. (1981a). Phaeophyta. In Clayton, M.N. & King, R.J. (Eds), Marine Botany: an Australasian Perspective, Ch. 5, pp. 104–137. (Longman Cheshire: Melbourne.)

CRIBB, A.B. (1960). Records of marine algae from south-eastern Queensland. V. Pap. Dep. Bot. Univ. Qld 4, 3–31.

MÜLLER, D.G., CLAYTON, M.N. & GERMANN, I. (1985). Sexual reproduction and life history of Perithalia caudata (Sporochnales, Phaeophyta). Phycologia 24, 467–473.

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

KEY TO GENERA OF SPOROCHNACEAE

1. Thallus branches slightly to distinctly compressed, usually with a faint, microscopic, midrib; sporangial sori at apices of branches, conical, surmounting a cup-shaped end to the branch, and bearing an apical tuft of assimilatory hairs which are readily lost

CARPOMITRA

1. Thallus branches terete; sporangial sori at the base of scattered, lateral, hair tufts, or surrounding the branches adjacent to or distant from the apical hair tufts, or with sporangia scattered amongst short, papillate, surface filaments, or unknown

2

2. Surface of branches covered with short (2 celled) papillate filaments, amongst which the sporangia occur in an extended surface sorus

NEREIA

2. Surface of branches smooth with a continuous cell layer, bare or bearing scattered, stout, long, basally meristematic assimilatory filaments or clusters of filaments with associated sporangia and paraphyses

3

3. Surface of branches with scattered, lateral clusters of filaments and associated sessile sporangia and paraphyses, or with adventitious, simple, scattered, trichothallic assimilatory filaments

4

3. Surface of branches smooth, with only terminal assimilatory tufts, and with dense sori surrounding branches with sporangia borne laterally on clavate paraphyses with larger terminal cells

5

4. Surface of branches smooth, bearing only lateral hair tufts with associated sessile sporangia and paraphyses forming loose sori

AUSTRONEREIA

4. Surface of branches bearing numerous, scattered, stout, simple, trichothallic assimilatory filaments; reproduction unknown

SPOROCHNEMA

5. Sporangial sori situated immediately below (or with a short sterile region) the apical hair tufts on determinate lateral branches

SPOROCHNUS

5. Sporangial sori situated some distance below the apical hair tufts, on indeterminate lateral branches or main axes

6

6. Hair tufts absent except when thallus growth active, but most branches with an apical cap; thallus much branched, fastigiate, wiry, with many erect fronds from a massive, "woody", holdfast becoming several cm across and 1–3 cm thick; sporangial sori on lesser branches

PERITHALIA

6. Hair tufts normally present, dense, conspicuous, 0.5–1.5 cm long; sporangial sori on larger branches

7

7. Branching umbellate, clustered at intervals of 3–15 cm, with long naked branches; hair tufts 1–2.5 cm long; sporangial sori surrounding branches, smooth

BELLOTIA

7. Axis percurrent, bearing long laterals, fringed with numerous short (5–15 mm long) branchlets, hair tufts 2–7 mm long; sporangial sori surrounding laterals and including bases of branchlets

ENCYOTHALIA


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