Tree Geometry: Parallel Lines

Among the illustrations between pp. 112 and 113 of Bernd Heinrich, The Trees In My Forest (New York: Cliff Street Books, 1997), a twig of the yellow birch exhibits parallelism of the type I discussed a few days ago:


In Heinrich's drawing of the hop hornbeam twig, counting from the bottom the second and fourth segments are nicely parallel, the first and third less so:


The trees in which these parallel twig segments have been noticed (European hornbeam, American hornbeam, yellow birch, hop hornbeam) are all members of the family Betulaceae.

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From western Maine, Beth writes appreciatively and perceptively about another book by Bernd Heinrich, A Year in the Maine Woods.