ABSTRACT
It has long been known that, in many species of plants, a proportion of the pollen grains in the anther of a given flower is abortive. This is true for plants in Nature, as well as for cultivated varieties. It is not possible to give a single or a simple explanation of this sterility and probably a large number of causes have to be considered. One cause has been frequently emphasised: as far back as 1832, Dutrochet 5 pointed out that pollen abortion is a criterion of hybridism, a view supported by Gaertner 6 , Many subsequent investigators have also adopted this view, but some more recent studies have shown that pollen sterility in a plant does not necessarily indicate a hybrid origin, although pollen sterility is frequently associated with hybridity.7,9,12
