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Polyxylon australe
Polyxylon australe T. Chambers, Regan Austral. J. Bot., 1986, 34(6): 677. 28 Jan 1987
- Name
- Polyxylon australe
- Rank
- Species
- Generic Name
- [Genus] Polyxylon
- Authors (Pub.)
- Chambers T. C.
Regan M. A.
- Publication
- Polyxylon australe - a new cladoxylalean axis from the Devonian of Australia [1987/1]
- Journal
- Australian journal of botany
- Annee/Jahrgang
- 1986
- Volume
- 34
- Issue
- 6
- Page number
- 677
- Year
- 1987
- Fossil Status
- stems
- Stratigraphy
- Upper Devonian
- Location
- Barraba, N.S.W., Australia
- Paleoregion
- Gondwana (Australia)
Data for Holotypus
- Repository
- National Museum of Victoria, Melbourne, Australia
- Repository Number
- NMVP161 996 + Slide Nos NMVP161 996 A, B, C
- Diagnosis
- Axes (10-25 mm diam.) are encased in a cortical layer of thick-walled sclerenchyma. The vascular cylinder consists of radially aligned arms of xylem, separated by a parenchymatous tissue of small cells, round in cross section with intercellular spaces; this tissue is continuous with and not differentiated from the central pith. Each arm of xylem bifurcates towards its outer region and each subarm often makes a further very short dichotomy. The protoxylem appears to be exarch at the outer tips of the xylem arms. Some of the arms of xylem interconnect across the pith by U-, Y- and W-shaped bridges. In cross section isolated bundles are seen in the pith; these also represent parts of the connections between the radial xylem arms. Tracheids of the metaxylem are 30-180 JLm in diam. and have alternately arranged circular bordered pits; those of the protoxylem are spiral and 12-30 JLm in diam. The phloem is presumably amphicribral; it is encircled by an endodermis with a casparian strip and each vascular segment is surrounded by another layer of cells with thickened outer tangential walls.
