Eucalyptus sieberiana kino collected within a few days of formation is composed almost entirely of polymeric polyphenols. The polymers appear to be largely made up of leuco-delphinidin units with ether linkages involving either or both of the C-3 or C-4 hydroxyl groups. The formation of leuco-anthocyanins by injured cambial tissues appears to be due to a blockage in the utilization of pyruvate in the tricarboxylic acid cycle.