Laurinoxylon ehrendorferi Berger, 1953a

Laurinoxylon ehrendorferi Berger, 1953a

Fig. 3 View Fig , photos a-i; Fig. 4 View Fig , photos a-i

Studied material. From the studied material, 17 samples of fossil wood collected from Aegean area, showed a similar lauraceous xylostructure of Type 2a ( Mantzouka et al., 2016), slightly different of the above described species. They were collected from late Oligocene to early Miocene volcano-sedimentary deposits and are registered and kept in the Collections of the Faculty Geol. & Geoenviron. of NKUA, under these field numbers: Aet 983, Aet 989, Aet 991, collected from Aetohory (Evros); Li 213, Li 214, Li 215, Li 218, Li 485b from Limnos island ; and Lsv 48, Lsv 50, Lsv 52, Lsv 56, Lsv 57, Lsv 392, Lsv 420, Lsv 421, Lsv 422 from Lesvos island .

Microscopic description. The growth rings – show quite indistinct boundaries, sometimes weakly marked by few rows of smaller flattened fibres, and by the start of the early-wood with normal-sized ground-tissue cells and large vessels.

The vessels – show in cross-section usually a diffuse-porous arrangement, only the vessels of final wood appear slightly smaller. The solitary vessels are numerous (around 50%), are round to oval-shaped and have the radial / tangential diameter of 100-200 / 70-170 µm. When grouped, usually as 2-3, the vessels are slightly deformed by compression and their wall thickness is of 7- 10 µm the double wall. Sometimes, in the final wood, the vessel lumen size is more diminished (to 70 / 40 µm r/tg.d). In longitudinal view, the perforation plates appear usually of simple type, more or less inclined and sometimes scalariform, with relatively few thin bars, up to 10-15 (in Lsv48, Lsv52). The intervessel pitting has an alternate arrangement, and the pits are polygonal, slightly rounded, and medium-sized with a diameter of around 10 µm. The vessel-ray pits have much-reduced borders to apparently simple, and are similar to intervessel pits, in size and shape. The cross-field pitting is described below. Helical thickenings in vessel elements are rarely present. The mean tangential diameter of vessel lumina is around 130 µm. Vessels density is of 20-40 vessels per square millimeter, or more. The mean vessel element length is more than 350 µm. Tyloses in vessels, sometimes present. Deposits in vessels usually not present.

Tracheids and vascular fibres/vasicentric tracheids usually absent.

The fibers – constitute the major part of the ground tissue. They appear sometimes septate and usually have few, small, simple or distinctly bordered pits.

The axial parenchyma – is present within the ground-tissue few of apotracheal type as diffusely dispersed cells among fibres and as scanty paratracheal or of vasicentric type. Their vertical walls have small simple pits. Sometimes, some parenchyma cells appear to be hypertrophied and full of mucilaginous substance, representing idioblasts.

The medullary rays – are usually fine: 1-3 seriate. Their height, in tangential sections, appear low to high, of 3 up to 25 cells, sometimes more, and the terminal cells appear triangular high, often flame-like. Radially, the cellular composition appear of heterocellular type, with body ray-cells all procumbent and one marginal row of taller cells, square and/or upright (of 4-12 µm), some of them as hypertrophied idioblasts, flame-like, globular to oval shaped, usually having bright or dark content. The cross fields with vessels show some small round pits, of 5-7 µm in diameter, in some horizontal rows arranged. Sometimes larger pits on the taller marginal fields can be observed. Ray density around 12 rays per tangential mm. Sheath cells and tile cells in rays are not present.

Storied structures – not present, neither to rays nor to the axial parenchyma and/or vessel elements. Secretory elements – appear as oil and/or mucilage hypertrophied ray-cells, as idioblasts associated with rays as are described above, and sometimes, associated with axial parenchyma. Mineral inclusions – absent. Intercellular canals – normal or traumatic axial or radial canals are absent.

Affinities and discussions. From the studied samples of petrified wood collected from Aegean area, mainland and insular, 17 specimens showed similar lauraceous structures of diffuse-porous type with quite indistinct ring boundaries, with numerous solitary vessels or in short radial multiples, vessels thick-walled with simple and sometimes scalariform perforations, with alternate intervessel pitting, also with scanty paratracheal to vasicentric parenchyma and with 1-3 seriate rays, heterocellular, having one marginal row of taller or upright cells, often hypertrophied, oval or flame-like, and full of oil and/or mucilage, representing idioblasts. But idioblasts appear associated with axial parenchyma too, even if, sometimes, is difficult to observe .

The xylotomy of the here studied specimens is in accord with the emended diagnosis of Laurinoxylon Felix, 1883 , emend. Dupéron et al., 2008. And, taking into account the location of the mucilaginous idioblasts as a main taxonomic indicator, after Mantzouka et al. (2016), it seems that we face a Laurinoxylon - Type 2a, with idioblasts associated with both ray and axial parenchyma. We will compare the here studied specimens with some lauraceous species described especially from the European and Mediterranean area.

Thus, Berger (1953a) described the species Laurinoxylon ehrendorferi , from the Aegean area, from Limnos and Tessaloniki, which show a xylotomy very similar to here studied specimens, as having frequently grouped vessels and idioblasts associated with ray parenchyma, but Mantzouka et al. (2016) suspected the presence of idioblasts associated to parenchyma cells and have considered this species as Laurinoxylon of Type 2a, similar to L. mueller-stollii Greguss, 1954 , to L. hasenbergense Süss, 1956 and to L. microtracheale Süss, 1956 (see Süss, 1958), all of them as Laurinoxylon - Type 2a, (see Mantzouka et al., 2016).

Thus, taking into account the xylotomy of the here studied specimens, with a structure marked by the presence of the typical idioblasts associated with ray parenchyma and with axial parenchyma too (even sometimes this is difficult to observe), and the similarity up to identity with the description of Berger (1953a) and of Mantzouka et al., (2016) for L. ehrendorferi (otherwise originally described by Berger as collected from Limnos), we assign the here studied specimens to the species Laurinoxylon ehrendorferi Berger, 1953a , as a possible ancestor of the current Persea L., a species that probably lived in the Mediterranean region during Cenozoic (see Kopp, 1966; and Persea - Wikipedia - accessed at 10.31.2023).