The Effect Of Ray Tissue On The Specific Gravity Of Wood


  • Fred W. Taylor


Rays, important tissues in all woods, may comprise as much as one-third of the total xylem of some species. This fraction of the wood, composed mostly of short parenchyma cells, is of little advantage in the use of wood except to enhance the appearance of decorative wood. A method of estimating the specific gravity of rays from measurements on the relative amount of cell wall substance is described, and estimated specific gravities are reported for the rays of several species.

The most significant report is that rays have a higher specific gravity than the surrounding wood composed of all the various woody tissues. The conclusion drawn from this observation is that increased ray volume may contribute to increased specific gravity. Hence, selection for high specific gravity may result in selection for high ray volume, which would most probably be undesirable.


Bannan, M. W. 1937. Observations on the distribution of xylem-ray tissue in conifers. Ann. Bot. (London) L: 717-726.nBannan, M. W. 1954. Ring width, tracheid size, and ray volume in stem wood of Thuja occidentalis. Can. J. Bot. 32(3): 466-479.nChalk, L. 1955. Ray volumes in hardwoods. Tropical Woods 101: 1-10.nClarke, S. H. 1930. The differential shrinkage of wood. Forestry 2: 93-104.nDeSmidt, W. J. 1922. Studies in the distribution and volume of the wood rays of slippery elm. J. Forest. 20: 352-362.nGoggans, James F. 1961. The interplay of environment and heredity as factors controlling wood properties in conifers with special emphasis on their effects on specific gravity. Tech. Kept. No. 11, School of Forestry, North Carolina State University at Raleigh.nGreenhill, W. L. 1949. The differential shrinkage of wood. Trans. A.S.M.E.: 66: 2: 152-154.nHarlow, W. H. 1927. The effect of site on structure and growth of white cedar (Thuja occidentalis). Ecology 8: 453-470.nHuber, Bruno and Gerhard Prütz. 1938. Über den Anteil von Fasern, Gefassen und parenchym am Authau verschiedener Hölzer. Holz als Roh- und Werksstoff 10: 373-381.nKennedy, R. W. 1968. Wood in transverse compression. Forest Prod. J. 18(3): 36-40.nMcIntosh, D. C. 1954. Some aspects of the influence of rays on the shrinkage of wood. Forest Prod. J. 4: 1.nMyer, J. E. 1922. Ray volumes of the commercial woods of the United States and their significance. J. Forest. 20: 337-351.nSchniewind, A. P. 1959. Transverse anisotropy of wood a function of gross anatomic structure. Forest Prod. J. 9(10): 350-359.nSchulz, H. 1962. On the effect of extreme growth conditions on the wood of various poplar clones. Holz als Roh- und Werkstoff 20(9): 347-357.nTaylor, F. W. 1968a. Variations in the size and proportions of wood elements in yellow-poplar. Wood Sci. and Tech. 3(2): 153-165.nTaylor, F. W. 1968b. Specific gravity differences within and among yellow-poplar trees. Forest Prod. J. 18(3): 75-81.nWeinstein, A. L. 1926. Summary of literature relating to volume, distribution, and effects of medullary rays in wood. J. Forest. 24: 915-925.n






Research Contributions