JAMA. 1966;198(12):1302. doi:10.1001/jama.1966.03110250116032.
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From Australia, Charles M. Stewart writes, "After extracting the required substances from the nutrient supply, the organisms often eliminate from their bodies the unused nutrients and always excrete, in some fashion, the waste metabolic products."1

This would be an utterly trite remark if it had been a statement about human physiology, but it was not. The subject was trees, and the author shows that the tree experiences serious problems in excreting its waste products. It must accumulate within its tissues most of the solid and liquid excretions. The heartwood center of the tree is composed of dead cells, and even the sapwood is composed largely of cells physiologically inactive. The tree, unable to discard and deposit its wastes in the byways of the soil, deposits them in its own body, and the death of the heart of the tree seems to result in part from the accumulation of the


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