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Summary The species Cynodon dactylon is enormously variable and has become truly cosmopolitan as a weed of disturbed habitats. Six botanical varieties are recognized in our classification, but only one is the widespread weed; the others are either narrow endemics or have restricted distributions. The great variability within the cosmopolitan variety appears to have been generated internally by genetic interaction of three of the six varieties and by fragmentation of the gene pool by translocation races.
Harlan et al. (Sat,) studied this question.