The lack of knowledge of treatability of timber species with pressure method may result in poor treatment in respect of penetration and retention of the preservative chemical Inwood. This knowledge for our indigenous timber species was not ascertained before. The relative penetrability of nineteen timber species was, therefore, determined with Lowry empty cell process using 40:60 creosote and light diesel oil mixture.

Specific gravity of species did not seem to have any bearing on the penetration cf preservative. Grain structure and presence of tyloses  appeared to be correlated with penetrability of the wood. The species were classified into four treatability groups according to the degree of heartwood penetrability.