Purified tannin from sorghum grain (NK 300) was provided by Dr. Haslam. Tannin from a high-tannin sorghum grain (BR 54) was purified by our standard technique (Hagerman and Butler, 1980) by A. Hagerman. Samples to be used for determining extinction coefficients were dried overnight over P205 at room temperature.Assays. Vanillin assays in methanol were carried out as recommended by Price et al. (1978), in a 30 °C water bath with a reaction time of 20 min. The vanillin reagent contained 4% concentrated HC1 and 0.5% vanillin in methanol. Absorbance was read in a Zeiss PMQ-II spectrophotometer, at 500 nm, the wavelength of maximum