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Electronic Flora of South Australia
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Electronic Flora of South Australia Family Fact Sheet

FAMILY UDOTEACEAE (Endlicher) J. Agardh

Phylum Chlorophyta – Order Caulerpales

Thallus either of tufted, subdichotomous filaments, or of interwoven filaments forming a compressed to complanate, simple or branched thallus differentiated into a medulla and cortex consisting either of filaments similar to the medulla or forming a surface layer of small, inflated "utricles". Heteroplastic, with chloroplasts and amyloplasts, wall containing xylan.

Life history diplontic with meiosis at gametogenesis as far as known; gametangia borne singly or in clusters on cortical filaments or utricles, anisogamous.

Taxonomic notes: Most genera and species of the Udoteaceae are tropical or subtropical, many being calcified (especially Halimeda). Eight genera occur along southern Australia, most with only a single species in this region.

References: The Marine Benthic Flora of Southern Australia Part I

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


1. Thallus filaments free, simple or branched, forming a loose tuft


1. Thallus of slender, interwoven or laterally attached filaments forming a macroscopic thallus, usually compressed


2. Thallus under 2 cm high, filaments slender (less than 60 µm in diameter), branched and constricted at their base, simple above


2. Thallus usually 5–15 cm high, filaments coarse (over 200 in diameter), subdichotomous above and constricted just above branchings


3. Thallus of flat, discoid or moniliform, calcified segments, joined by narrow, uncalcified nodes


3. Thallus slightly compressed and subdichotomous, or tufted, or complanate and felt-like, simple or branched


4. Thallus subdichotomous, branches 2–3 mm broad, slightly compressed, cortex of small "utricles"


4. Thallus simple or branched, loosely tufted or complanate, usually more than 5 mm broad (Rhipilia may be less broad)


5. Thallus much branched, with subdistichous, lateral branch tufts of filaments of elongate, regularly constricted segments with almost complete cross walls; lower axes with dense cortex of moniliform filaments


5. Thallus usually simple, tufted or flabellate to ovate and several filaments thick, spongy


6. Thallus to 1.5 cm high and 0.5 cm across, of loose tufts of filaments with occasional tenacula connecting lower filaments


6. Thallus over 2 cm high when mature, compressed, spongy, several filaments thick, with a distinct stipe and lamina; filaments either not connected laterally or connected by circular areas with or without protrusions from the segment


7. Thallus (1–) 2–8 cm high, stipe short, filaments attached laterally by circular areas with or without protrusion from the segment


7. Thallus 8–20 cm high, with a long stipe expanding into the flabellate lamina, consisting of entwined filaments not laterally attached


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