A comprehensive review of the karyotype in plant systematics was pub­ lished by Lewitsky (83) 40 years ago under this same title. He was dissatis­ fied with the narrow use of meager karyological data and included his own more complete work on several genera of the Ranunculaceae subfamily Hel­ leboreae. He chose a group of genera showing distinct systematical relation­ ships both among and within the taxa with the further advantage that a detailed morphological study of the subfamily had been completed some 20 years before. There was thus a good opportunity for a comparison of the morphological and cytological findings. Lewitsky's general conclusions may be summarized as follows. The idea of the karyotype as a characteristic especially and exclusively applied to generic definitions or to any other systematic unit is not tenable. A particl1lar karyotype may be associated with a complex of characters circumscribing a family, tribe, genus, species, or race. When certain peculiarities such as size of chromosomes and basic number are concerned, their corrcspondcnce to higher taxonomic subdivisions does not imply that they did not derive from lower categories; it only indicates a greater phylogenetical stability of these peculiarities. Changes in chromosome morphology may lag behind or precede change in external phenotype. Close morphological similarity of taxa associ­ ated with great differences in the basic karyotype suggests that cytological differences have been by sudden fragmentations, translocations, etc. Partial correspondence of morphology and karyotype implies parallcl changes. From his studies in the Ranunculaceae, Lewitsky pointed out the general parallelism of more symmetrical b.ryotypes with primitive characters and asymmetrical karyotypes with specialized forms. Although reorganization of the karyotype has been discussed in terms of cytogenetics by several workero, White (162) was the first to present a lu­ cid account of karyotype evolution in animals, and Stebbins (140) has dis­ cussed the data for plants. The development of techniques for the study of vertebrate somatic chromosomes has brought about a veritable flood of ka­ ryotype papers, many of which are largely descriptive, showing the lack of a