Attention is drawn to the economic importance of triploidy in Citrus. During his investigations, the author only found one tetraploid (2n = 36) and one pentaploid (2n = 45) as natural polyploids in Citrus. Preliminary results are then presented of an experiment to produce polyploids through the treatment of seeds with colchicine. Germination was not influenced by these treatments. Chromosome counts in root tips and the mensurement of stomata area gave the following results : 1) Three of the examined plants (C.3, C.9 and C.15) had diploid and tetraploid roots and a tetraploid epidermis, to judge from its stomata area. 2) Another plant, C.12, besides being an hyperdiploid (2n=19 and 20?), had one root which was a chimera, as in one of its cells approximated 38 chromosomes were counted; in spite of this chromosomal alteration, the epidermis of its leaves were of normal size, as in diploids.