Part 2. Needle characters

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Abstract
Morphological and anatomical characters of the needles were examined as part of a study of variation in the natural populations of Pinus radiata. Although the species is normally three-needled, trees bearing a proportion of binate fascicles occur in all populations, but cannot easily be defined as a distinct class. There is a relation between needle number and the radius of the fascicle. Compared with those at Monterey, trees in the Cambria population have significantly longer and thicker needles, with more widely spaced stomatal rows and marginal teeth. Needles from Año Nuevo Point trees are intermediate in all these respects except the spacing of the marginal teeth. Resin canals vary from 0 to 2 per needle in all populations, and the whole range of variation is often found in samples from individual trees. The other anatomical features investigated, namely, the number of vascular bundles, the structure of the hypodermis, and the shape of the stomatal cells, show minor variation in all populations.

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