axis of S. brevistigma, in which cortical parenchyma forms an extensive aqueous tissue.
The primary cortex is characterised by an assimilatory tissue which is formed of parenchyma except in L. spartium where it consists of a 4-6 cell thick arm-palisade tissue. The cortical paren- chyma in S. brevistigma is composed of an extensive tissue of thin- wailed, elongated colourless cells with probably a water-storage func- tion and is strengthened by small scattered groups of stone-cells (fig. 199).
Secretory cells with tanniniferous contents occur in the cortex, in the broad medullary rays and in the pith of L. spartium (fig. 200 G.) They are also found in the cortex of G- varians and in the cortex, soft bast and pith of P. cyyianckoicles. Numerous clustered crystals of oxalate of lime occur in the cortex and soft bast of P. cijnanchoides. The pericycle is composed of closely placed groups of stone-cells, except in G. varians in which it consists of groups of bast fibres with large lumina.
The groups of stone-cells are rhomboidal in P. spartium and S. brevistigma ; they are thin and long in P. cynanchoides. Bast fibre groups in G. varians are rhomboidal.
Structure of wood can best be understood from the following tabular form.
