Cover illustration: Branch junctions in Douglas-fir trees from a study of flow through the junctions. The inset on the right shows a junction that was stained by sealing the upper right branch and applying a partial vacuum to the upper left branch while safranin entered the main stem from below. The three insets on the left show the resulting staining patterns observed on transverse and longitudinal faces of the stem at three points below the junction. (See Schulte and Brooks, pp. 1597-1605.)
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