Varying Structure of Conifer Leaves in Different Habitats

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Abstract
The leaves of 3 spp., Abies lasiocarpa, Picea engelmanni and Pinus contarta, were studied. Specimens were examined of different ages and from 3 habitats, alpine, mesic and xeric. Needles of Abies are longest, widest and thinnest, those of Picea longest with smallest cross-section, those of Pinus largest in all dimensions in the mesic habitats. Thickness of cuticle and epidermal cell walls is greatest in xeric and alpine habitats. Stomatal pits tend to be deeper in xeric habitats except in Pinus. Intercellular space in the chloren-chyma varies both with the age of the needles and with habitat. There is an increase in the size and number of cells of both xylem and phloem, produced by growth of a cambium; the increase is greater in the phloem. The oldest needles were found in mesic habitats.