In an investigation of fibre lengths within one tree ofEucalyptus regnans, 50 years old and 172 feet high, particular attention was paid to the variation throughout a growth ring and it has been found that the fibres of the last-formed late wood were consistently longer than those of the early wood. The fibre length in the late wood varied throughout the tree from 0.6 mm. in the ring next to the pith at all levels to 1.35 mm. in the outermost rings at the 50 feet level. At all levels there was a rapid increase in length of both early and late wood fibres from the centre of the tree outwards for approximately 10 growth rings, after which a more or less constant value was reached in each case. The need for care in selecting material for comparative fibre length measurements and in recording results has been stressed.
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