Abstract in English:In order to study the susceptibility of the various stocks with regard to the new disease "tristeza" ("sadness"), a quick and acurate identification of the stock is required. In orchards this cannot be done in most cases as stocks do not always exhibit sprouts and on account of erroneus information frequently given by owners. We have tested the colorimetric identification, already employed in other countries. This identification is based on the differences of color obtained in the watery extract cf the bark taken from the trunk or from the root, when treated by special reagents. The results obtained are somewhat different from those described by the authors of the method. This is perhaps due to variation in environmental conditions. Only the Almen and ferric chloride tests gave satisfactory results, making it possible to arrange the species and varieties examined into four groups : (1) C. aurantium L. ; (2) C. sinensis Osbeck; (3) C. limonia Osbeck ("gigante" variety) and (4) all the others. Although deficient in certain respects the test is valuable, permiting us to identify the stocks of orange trees, azeda as well as caipira the most employed in the citrus orchards of the State of S. Paulo.