1. The chromosome numbers of 116 plants of orchard grass were determined from root tips. Twenty-two per cent had 27 chromosomes, 59 per cent 28, 12 per cent 29, and 8 per cent 30. One plant out of ten in tall oat grass had 27 chromosomes, and one out of six in crested wheatgrass had approximately 31 chromosomes, while the rest were normal (2n = 28). 2. In all three species the chromosomes were associated in pairs at mid-prophase of the first division, but frequent exchanges of partners indicated some quadrivalent formation. Occasionally a single pair of homologues were associated throughout their entire length. 3. The number of quadrivalents per microsporocyte varied from 1 to 7 in each species. For three plants of orchard grass the range in average quadrivalent frequency was 3.3 to 4.2 with an average of 3.9; for five plants of crested wheatgrass it was 3.4 to 4.2 with an average of 3.7; and for nine plants of tall oat grass it was 3.4 to 4.5 with an average of 3.8. 4. The percentage of ring and chain qu...