CPYSTALS IN SOME THAI COMMERCIAL WOOD TO HAVE A DULLING EFFECT ON TOOLS

Abstract

A collection of some crystal-bearing Thai commercial wood, belonging to 41 genera of 22 families, was made with reference to the distribution and type of crystals in containing cells. The occurrence of crystals is diagnostically important in seperating closely related species. When there are crystals abundantly present, they may have a dulling effect on tools. In some genera, there are modifications of the crystals-containing cells which are enough consistent and to form as useful key to families sometimes to genera. These are: (a) presence of crystals in enlarged cells, (b) the presence of a number of crystals of various size and shape in one cell, (c) changes in the cell wall, causes of cells become sclerosed.

The study which was terminated in 1982, aimed to avoid timber which may have abundantly crystals. The results of the 4 years of exhaustive search had been compiled in this terminal report along with available crystals on the Appendix table.

The following types of crystals are found.

1. Rhomboidal crystal, square or diamond-shaped. These are the most common of all crystal types. They may occur singly, two or more per cell. These are commonly deposited either in the rays and for axial parenchyma in species of many families.


2. Druses crystals, spherical clusters either attached to the cell wall by a peg or lying in the cells. These are present in Terminalia spp, of the family Combretaceae.


3. Acicular, Needle-shaped crystals which are often small, free in and do not fill the cells. These are deposited in ray cells of many species of the Verbenaceae.

These research is significant in that it raises possibility of protection of a dulling effect on tools before lumbering, a possibility that points to further research which may have new Technology in order to solve this problem.