A trisomic mutant of M. incana appeared in F1 from a varietal cross. This type, named "Small," has numerous, small, flat, and rigid leaves as compared with related plants with normal chromosome number (7II). Its extra chromosome is undoubtedly a fragment. In the reduction division the unpaired fragment either divides at the 1st division and segregates at the 2nd or vice versa. It usually reaches the poles of the spindle later than the paired chromosomes. Three of the progeny from selfing of the Small mutant showed the Small characteristics to an extreme degree. Two of these were tetrasomic diploids (7II +2 fragments); the other was a disomic haploid (7I + 1 fragment). It is concluded that similarity between haploid and tetrasomics was due to the balance between whole chromosomes and the fragment or fragments being the same in both. The pollen mother cells of the disomic haploid plant were about 1/2 the size of those in tri- and tetrasomic diploid Small. All chromosomes in the haploid usually divided equationally, giving rise to dyads (70% of cases), but assortment was also observed. The 2 fragments in the tetrasomic diploid examined were sometimes though not always paired.