Electronic Flora of South Australia Family Fact Sheet

TRIBE ZONARIEAE De Toni

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae

Thallus flabellate and simple or lacerate, or subdichotomously or irregularly laterally branched, or much branched with thickened terete axes bearing small bicuspid laterals; transverse section 2–10 cells thick, cells of similar size or not, regularly or irregularly arranged, with a distinct or vague cortex and medulla. Growth from a row or cluster of apical cells forming the apical margin of the frond.

Reproduction: Reproduction: with the sporophyte producing scattered or clustered sporangia on or in the cortex, with one, four or eight (meio)sporangia, and by separate female and male thalli with oogonial and antheridial sori.

Taxonomic notes: The marginal row of apical cells readily separates most genera from members of the Dictyoteae. However, Dictyopteris has an apical cluster of such cells and Lobospira a row of 8–12 cells at the apex of the indefinite branches (not in the bicuspid laterals). Most but not all genera are also distinguished by the regularity and similar size of cells in transverse section of the thallus; in longitudinal section, the segmentation from the apical cell is of importance (Abbott 1977).

References:

ABBOTT, I.A. (1977). On the identity of Zonaria hawaiiensis (Phaeophyta, Dictyotales). Bull. Jap. Soc. Phycol. 25, 1–8. (Mem. Iss. Yamada.)

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 ZONARIEAE

1. Thallus much branched, with thickened axes 0.5–1.5 mm broad bearing, spirally along the axes, bicuspid laterals 1–3 mm long; apices of axes with a row of 8–12 apical cells

LOBOSPIRA

1. Thallus simple, flabellate or lacerate, to moderately branched with elongate laterals, usually complanate, (2–) 5–20 (–50) mm broad; growing margins usually with long rows of apical cells (shorter rows in Dictyopteris and Spatoglossum)

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2. Thallus simple to lacerate, with a circinnately inrolled apical meristem

PADINA

2. Thallus simple to much branched, with the apical meristem flat

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3. Thallus with a prominent thickened midrib throughout each branch

DICTYOPTERIS

3. Thallus without a thickened midrib

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4. Thallus 2 cells thick throughout

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4. Thallus (2–) 4–10 cells thick in mature parts

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5. Sporangia scattered, thallus much divided, (5–) 10–20 cm high, stupose basally

CHLANIDOPHORA

5. Sporangia grouped into sori, thallus flabellate or multifid, usually 3–6 cm high

DISTROMIUM

6. Cells in transverse section of old parts of thallus not in regular rows of even size, thallus 2–4 (–6) cells thick, medullary cells commonly more than 25 µm across in transverse section

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6. Cells in transverse section of all parts of thallus in very regular rows, cells of even size (except the central row in Lobophora and in some taxa the cortical cells), thallus 5–10 cells thick, medullary cells generally less than 25 µm across in transverse section (except central row in Lobophora)

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7. Meristem a localised cluster of apical cells; cells in transverse section of thallus irregular, with cortical cells subdividing; sporangia scattered, formed from cortical cells and not protruding from thallus surface

SPATOGLOSSUM

7. Meristem a broad marginal row of apical cells; cells in transverse section of mid thallus regular, becoming irregular, with cortical cells the same size as inner cells; sporangia scattered or grouped, protruding above the thallus surface

TAONIA

8. Cortical cells mostly single (not paired) above each medullary cell in transverse section of thallus; sporangia with one or more stalk cells, producing four spores

HOMOEOSTRICHUS

8. Cortical cells mostly paired above each medullary cell in transverse section of thallus; sporangia without a stalk cell, producing eight spores

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9. Medullary cells in transverse section of thallus of similar size throughout

ZONARIA

9. Medulla with a central row of distinctly larger cells

LOBOPHORA


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