SUMMARY1The main taxa of the genusDactyliaare surveyed, illustrating the range of species and subspecies occurring in the group.2The phenotypic characters in nineteen populations, including diploids and tetra‐ploids, were analysed in detail; there were large genetic differences between the populations.3The within‐population correlation of characters was studied and found to vary independently.4The heritability of some taxonomically‐important morphological characters was measured, e.g. panicle length, flag‐leaf length, and lemma apex. Each was highly heritable, and capable of independent response to selection.5The between‐population correlation of morphological characters was studied. The components of panicle size, flag‐leaf length, and lemma apex were related, showing a similar trend in diploids and tetraploids.6The significance of the trend of variation is discussed in relation to taxonomy an