The initiation and development of the leaves of Douglas fir is described in detail. Leaf initiation is similar to that of other foliar organs and involves both protodermal and peripheral cells of the apex. Apical and subapical initials are present but active for only a short time. Most enlargement is a result of intercalary cell division and enlargement. A limited marginal meristem is present. No differentiation of tissues occurs before bud dormancy in the fall. Growth following dormancy shows the various tissues to mature at different rates and all tissues are fully mature when the leaf becomes dormant in the fall. Growth periodicity of the shoot apex and the length of the growing season are discussed. Initiation and development of leaves in relation to all other foliar organs in Douglas fir are compared.
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