Characteristics of the xylem

Annual rings can be distinct or indistinct. Ring boundaries are marked by marginal, multiseriate rows of rectangular thick-walled fibers (Figs. 1 and 2). The xylem is diffuse-porous with solitary vessels (Figs. 1 and 2). The earlywood vessel diameter varies between 30-50 pm and vessel density is between 300-500/mm2. Vessels contain simple perforations and thin helical thickenings. Inter-vessel pits are predominantly large and round and arranged in alternating position. Radial walls of fibers are perforated by large pits (ca. 3 pm; Fig. 3). Fibers are thin- to thick-walled (Fig. 2). Parenchyma is mainly apotracheal diffuse in aggregates. Rays are 2-3-seriate (Fig. 4), and are heterocel-lular with 4-6 rows of upright cells (Fig. 5).

Fig. 3. Fibers containing large pits with slitlike apertures. Stem, shrub, maccia, Mediterranean climate, Mallorca, Spain. Myrtus communis, radial section.

Left Fig. 1. Diffuse-porous wood with distinct and indistinct or growth zones. Stem, shrub, maccia, Mediterranean climate, Mallorca, Spain. Myrtus communis, transverse section.

Right Fig. 2. Diffuse-porous wood. The growth zone boundary is formed by thick-walled, rectangular fibers. Large vessels occur at the beginning or in the middle part of the ring. Stem, shrub, maccia, Mediterranean climate, Mallorca, Spain. Myrtus communis, transverse section.

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Fig. 5. Heterocellular rays with some central procumbent cells and some marginal upright cells. Stem, shrub, Mediterranean climate, Mallorca, Spain. Myrtus communis, radial section.

Fig. 3. Fibers containing large pits with slitlike apertures. Stem, shrub, maccia, Mediterranean climate, Mallorca, Spain. Myrtus communis, radial section.

Fig. 4. Uniseriate rays with axially elongated cells and 2-3 heterocellular rays with round central cells and elongated marginal cells. Stem, shrub, maccia, Mallorca, Spain. Myrtus communis, tangential section.

Fig. 5. Heterocellular rays with some central procumbent cells and some marginal upright cells. Stem, shrub, Mediterranean climate, Mallorca, Spain. Myrtus communis, radial section.

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