Summary(1) The chromosomes of 72 species ofTulipahave been counted. The majority are diploids (n=12), but one pentaploid, ten tetraploids, and six triploids have been discovered.(2) In one instance the smae species has been found to exist in pentaploid, tetraploid, triploid, and diploid forms, the triploid having been produced experimentally by hybridization between tetraploid and diploid.(3) Aneuploids have been produced experimentally, but are not known among the species or garden varieties. In two species fragmentation has been observed.(4) The morphology of the chromosomes is of service in determining the taxonomic groups within the genus.