Much of the technical information contained in this volume has been derived from tests at the Building Research Establishment, Princes Risborough Laboratory, or at similar research institutions. Laboratory tests are necessarily on a limited amount of timber. Although care is taken to obtain as nearly as possible average material for test, it should be understood that the properties of any timber are liable to considerable variation according to conditions of growth. Paragraphs concerned with the description of the trees and the natural distribution of the species have necessarily been based largely on published information. Information concerning uses has been compiled from many sources. Though care has been taken to obtain confirmatory evidence, wherever possible, of all information from outside sources, the Laboratory cannot vouch for its absolute accuracy. In cases of doubt, however, the policy has been to err of the side of caution.