Flash pyrolysis of the outer cortical tissues in Lower Devonian Psilophyton dawsonii

Coalified residues of the xylem and peripheral structure tissues (stereome) from permineralized (CaCO3) Lower Devonian Psilophyton dawsonii have been analysed by flash pyrolysis-gas chromatography-mass spectrometry. Both yielded C-0-C-1 alkylphenols, C-1-C-3 alkylbenzenes, C-0-C-1 alkylnaphthalenes, although with varying relative abundances. The stereome also generated a series of n-alk-1-enes and n-alkanes (C-8-C-24, maximum at C-10) which is believed to be derived from the cuticle. The sources of the aromatic compounds are discussed, and while it is concluded that those in the xylem are dern;ed from lignin, the macromolecule having been degraded by diagenesis and thermal maturation, the molecular sources of those from the stereome may also include a wide range of substances including simple phenolic acids, flavonoids and non-lignin polyphenolics. Possible functions for the stereome are discussed. (C) 1997 The Linnean Society of London.