2. In Tripsacum hybrids with maize the number of Tripsacum chromosomes can be determined by an examination of the pollen. Plants with 20 Zea chromosomes plus one Tripsacum chromosome have 50 per cent normal and 50 per cent small pollen. Plants with two Tripsacum chromosomes have 25 per cent normal, 50 per cent small, and 25 per cent empty pollen. Apparently a single Tripsacum chromosome causes reduction in size while two or more cause complete abortion of the pollen. Extra chromosome plants can be readily identified in the field by pollen examination. We now have a large number of stocks all having 20 maize chromosomes and one extra Tripsacum chromosome. We are attempting to identify these extra Tripsacum chromosomes by crossing with corn stocks in which the chromosomes are marked by two or more recessives. We are badly in need of multiple recessive stocks for this work.