1. Analysis of chromosome types in Crepis biennis reveals the existence of a double basic genom containing 5 distinct types, with 2 representatives of each type which differ in certain details. This indicates that C. biennis may be an allo-octoploid which originated through hybridization between two 5-paired ancestors which differed somewhat in chromosome morphology. Available evidence an the meiotic behavior of biennis chromosomes indicates that the putative parents were subspecies of the same species. The most likely process of origin is through hybridization followed by amphidiploidy and then a second doubling.
2. In C. ciliata a similar situation is found, but the differentes between the 2 representatives of each of the 5 different chromosome types are less marked. This species may have had a similar origin to C. biennis or it may be an auto-octoploid in the stritt sense.
3. The evidence an origin of these two species adds further proof that 5, not 4, is the original number in Crepis.
4. Tetraploidy is the antecedent of autosyndesis and allo-polyploidy in one or both parents is sometimes associated with autosyndesis in species hybrids. By analysis of such Gases it is possible to derive working hypotheses as to the genetic nature of polyploid species which may lead to further knowledge concerning their nature and origin.