Cytology and cytogenetics as a fundamental taxonomic resource for the 20(th) and 21(st) centuries

The status of cytological and cytogenetic data as evidence of value in taxo nomic decisionmaking and biosystematic investigations over the past 50 year s is surveyed. The main headings considered are chromosome number, genome s ize, chromosome morphology, chromosome staining characteristics. chromosome and genome disposition in the cell, and chromosome behaviour and homology, The main conclusions are that many of the exciting new developments at the borders of cytogenetics and molecular biology (molecular cytogenetics) are producing a wealth of new data of enormous taxonomic and evolutionary impo rtance, but that for these to reach their full impact it is essential that they are fully integrated with traditional cytological data, the need for w hich remains as great as ever.