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Ch.23 Seed Plants I: Seed Plants Without Flowers ("Gymnosperms")…
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Cross Connection: Wood of pine, like that of all conifers, lacks vessels; it consists almost exclusively of tracheids. Growth rings are visible because late wood contains narrow, thick-walled tracheids, whereas early wood contains wide, thin-walled tracheids.
Cross Connection: In seed cones of pine, all parts are fused together; even the bract is fused to the oviluferous scale. When morphologists first began working on pine cones without knowing about fossil structures, they were completely baffled and could not explain such complex structure.
Cross Connection: The long three-pointed bracts of a Douglas fir cone are the true leaves of the cone axis. Each one contains an axillary bud whose leaves have fused together side by side into the flat, sheidlike ovuliferous scale just behind each bract. These fused leaves that constitute the ovuliferous scale are actually megasporophylls.
