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A study of the estimation of sugars in the complex mixtures in plants was commenced by Brown and Morris,2 followed by the work of Parker3 and the more complete studies of the Rothamsted group.4 These workers have tested many points of procedure of the analytical details in the cupric reduction methods and it is apparent that the difficulties have been dearly recognized. Ehen such skilled and careful workers as Brown and Morris considered the degree of accuracy as being equivalent to 1 mg. of the cupric oxide weighed, corresponding to 0.5 mg. of glucose.One of the chief objections to copper reduction methods is the 'difficulty in securing absolute uniformity in the conditions of reduction, which is so essential, since Nef5 has shown that a number of products, variable in nature and quantity with the concentration of the sugar solution and alkali are formed when the sugar molecule is acted upon by alkaline Fehling solution. The main sources of error due to (a) lack of temperature control and (b) auto-oxidation have been largely overcome by Quisumbing and Thomas ;6 notwithstanding which, considerable difficulty was experienced in our Laboratories in applying it to the determination of small quantities of sugar in leaves and spurs of apple trees, in connection with biochemical studies relating to the effect of fertilizers on the physiological functions of the apple.7A combination of the gravimetric and volumetric methods (Bertrand) is quite extensively used a t the present time in biochemical laboratories. The procedure introduces the errors of both; moreover, it is not generally recognized that the standard permanganate solution must be standardized 1 Read a t the Milwaukee meeting of the American Chemical Society, September, 1923.The cost of this investigation has largely been defrayed by a grant from the A d a m Fund for Agricultural Research.

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