千屈菜
In tristylous species, incompatibility varies, with some species showing varying degrees of compatibility outside of the reciprocal herkogamy pattern of pollination.  Darwin noted weak incompatibility commonly occurring in the M-morph of "Lythrum salicaria." Some species have shown weak or absent incompatibility in their mating system, however self-compatibility in tristylous species is still poorly understood. Research on "Eichhornia paniculate", found difference in pollen tube growth between intra- and inter-morph pollen, indicating that the incompatibility system is a case of cryptic self-incompatibility.