A range of mechanical and physical properties were carried out on 96 specimens of Chestnut wood and on wood types ranging from "compression" to tension wood; tests included (1) growth stresses, (2) longitudinal Young's modulus in green and air-dried conditions (3) shrinkage in longitudinal and tangential directions. Anatomical observations permitted determination of the proportion of fibres with a gelatinous layer. The influence of these atypical fibres on macroscopic wood properties is examined and discussed. A basic model is proposed to determine their properties in theoretically isolated conditions.