Three strains ofOenothera hookeri bi. klbl. were investigated for their tannin content. The tannins could be detected by reactions with gelatine-sodium chloride-, lead acetate- and ferric chloride-solutions and by adsorption on skin powder. Furthermore the tannins found were shown to be mostly hydrolysable; condensed tannins are scarcely present. It is unlikely that phlobaphenes are present. The tannins found are distributed systemically. On the average the fruits and leaves contain most of the tannins sometimes up to 16 per gram dry weight. The shoots and flowers contain about 8, and the seeds and roots have only 2–6. The tannin content of younger leaves is lower than that of older ones. The results are discusse
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