SIZES, DISTRIBUTIONS, AND NUMBERS OF VERTICAL RESIN DUCTS IN LODGEPOLE PINE

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Abstract
Methods are described for easy detection of vertical resin ducts in Pinns contorta Dougl. var. latifolia Engelm. Also a photographic method for determining the area and circumference of growth rings is described. The time of vertical resin duct formation was the same in both slow- and fast-growing trees. Vertical ducts seldom occurred in radial alignment in consecutive years. The diameters of vertical ducts varied from 60 to 105 μ and were least near the pith; lengths ranged from 3.8 to 43.2 cm in a 75-year-old tree and 1.2 to 12.0 cm in a 30-year-old tree. Wide variations occurred in the abundance of vertical ducts between years. Their presence in large numbers in one year appeared to influence their abundance in the following year. The fluctuations in number occurred simultaneously in all trees examined. Radial growth was not associated with these fluctuations. There was circumstantial evidence for a direct relation between high summer temperatures, large cone crops, and large numbers of vertical ducts.

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