The present investigation deals with the cytological nature of a bud variant which originated on a progeny tree of a hybrid mandarin (King x Dancy). From the variantbranch several progeny trees were grown in comparison with others derived irom the normal part of the tree. The results of extensive investigation indicate that the budded progeny of the variant branch includes at least two types of chimeral constitution : one is 2n-4n-4n respectively for its first, second, and third germ layers, and the other is 2n-4n-2n for the same layers. On the assumption that three germ layers exist in Citrus, it was demonstrated that the first germ layer forms the epidermis, the second one all leaf tissues (with the exception of the epidermis), the microsporocytes and at least part of the cortex of young vegetative shoots, and the third one forms the procambium, cambium, and the pith of the stem. Determination of chromosome number in root tips of cuttings of these two chimeras, demonstrated that these roots, at least when they derive from a callus, have their origin in the third germ layer. Comparison of stomata of mature leaves of different plants indicates that size differences, even if they are of statistical significance, are not always due to differences in chromosome number in the epidermis. The progeny trees of these chimeras differ considerably in growth habit, the one with a diploid third germ layer being approximately normal (erect), the other with a tetraploid third layer being low and broad. This fact suggests that the third layer plays a considerable role in determining the growth habit of the trees. Both chimeras are rather unfruitful, which is typical for Citrus tetraploids.