Electronic Flora of South Australia Family Fact Sheet

FAMILY CYSTOSEIRACEAE Kützing

Phylum Phaeophyta – Order Fucales

Thallus usually 20–150 cm long, with 1–3 simple or branched stipes bearing radially, distichously or tristichously branched axes or primary branches, straight to flexuous, each slightly to much branched with usually (sub-)determinate laterals some of which may develop further; laterals simple or branched, terete to flat; holdfast discoid-conical, or lacerate, or subhapteroid, rarely becoming stoloniferous. Vesicles present or absent, subspherical to ovoid, discrete or within the branches. Growth from a single, three-sided, apical cell in an apical depression. Structure with medulla, cortex and surface meristoderm.

Reproduction: Thalli monoecious or dioecious. Receptacles developed from the whole or the upper parts of the laterals or their ramuli, terete to flat, elongate. Conceptacles and their ostioles scattered or on the surface or margin of flattened receptacles, unisexual or bisexual; oogonia sessile, without a mesochiton collar, containing a single egg; antheridia sessile or on branched paraphyses.

Taxonomic notes: A family of about 16 genera, with 9 in southern Australia, distinguished by their single, three-sided, apical cells, receptacles developed from the ramuli, and oogonia with a single egg.

References: The Marine Benthic Flora of Southern Australia Part II

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 CYSTOSEIRACEAE

1. Branching radial, branches terete or winged

2

1. Branching distichous from axes or from margins of flattened fronds

6

2. Upper branches terete and verrucose, covered with laterally appressed, short, peltate, determinate laterals containing vesicles and conceptacles

SCABERIA

2. Branches smooth or muricate, but not covered with dense peltate laterals; lesser branches developing into receptacles

3

3. Branches containing vesicles and with triquetrous wings, with conceptacles developing in the wings

HORMOPHYSA

3. Branches terete, without wings, conceptacles developing in ends of ramuli; basal ramuli terete, not leaf-like (in southern Australian Cystoseira)

  4

4. Thallus with a short main stipe and long primary branches; vesicles within the ultimate ramuli, in series of (1–) 2–3 (–4)

CYSTOSEIRA

4. Thallus with long axes or primary branches from the holdfast, without a short main axis; vesicles absent or borne singly on the primary branches

5

5. Vesicles borne directly on the primary branches, replacing ramuli; branching radial; receptacles 1–2 cm long, developed from ramuli

CAULOCYSTIS

5. Vesicles absent; branching at first tristichous, becoming irregular; receptacles 2–6 mm long, formed from ends of ramuli

ACROCARPIA

6. Thallus with strongly developed, flexuous, axes bearing alternately distichous laterals of limited growth from the face or edges of the (usually) compressed axes; laterals simple to repeatedly branched, distichously, radially or irregularly; secondary (and tertiary) axes arising in axils of primary laterals; vesicles present or absent; conceptacles on terete ramuli or on margins of compressed ramuli

CYSTOPHORA

6. Thallus irregularly subdichotomously or laterally branched in one plane, with or without flexuous axes or limited laterals; vesicles absent; conceptacles on the edges or surface of compressed to flat branches

7

7. Holdfast stoloniferous, often proliferous; branching fairly regularly pinnate, relatively thick

PLATYTHALIA

7. Holdfast discoid-conical or divided; branching irregularly lateral to pinnate, either thick or relatively thin

8

8. Thallus with a short, simple, unbranched stipe, bearing complanate, not or vaguely costate, fronds with irregularly alternately branched, flat, entire, relatively thick laterals

CARPOGLOSSUM

8. Thallus with an erect, dichotomous, subterete, perennial stipe, bearing annually relatively thin, flat, costate, alternately to dichotomously branched fronds, usually with a midrib and spinous margins

MYRIODESMA


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