9. In the progeny of a plant trisomic for chromosome 6 there occurred an individual with 20 chromosomes plus a fragment composed of the long arm of chromosome 6. The insertion region is apparently terminal. Studies of the disjunction of the two normal chromosomes 6 and the fragment, utilizing the technic of McClintock in studying the number of nucleoli in the quartets of microspores, showed that in 2.4% of the cases the fragment chromosome went to one pole and the two normal chromosomes to the other pole. In the remaining cases the two normal chromosomes underwent disjunction.