A novel heteromorphic phenotype, P*, in Primula × tommasinii differs from long-styled (‘pin’) morphs, half the pollen having a size distribution typical of pins and the other half a distribution typical of short-styled ‘thrums’. All P* pollen is compatible with pin mothers, and is compatible on P* stigmas, but is incompatible with thrum mothers. However, as a mother, P* shows the same compatibility relationships as do pins. The P* phenotype is inherited as a single dominant factor. All P* plants are heterozygous for the recessive ‘pin’ chromosome, but the offspring of P* selfs give ratios of 2:1 P*: pin, rather than 3:1. All P* plants have styles, stigmatic papillae and style cells shorter than pins, but much longer than in thrums. We conclude that this phenotype results from a recombination within the heteromorphy supergene between a locus which controls pollen size and one which controls dominance for pollen size. On the P* recombinant chromosome we suggest that loci controlling female compatibility and style length (in part) (G/g), anther position (A/a), and pollen size dominance (Mpm/mpm) carry recessive, pin-linked alleles; whereas those controlling pollen size (Pp/pp), male compatibility (Pm/pm), and style length (in part) (Gm/gm) carry dominant, thrum-linked alleles. A recessive, thrum-linked lethal l is also linked to this part of the chromosome. Thus, it appears that at least seven loci control the Primula heteromorphy supergene. We also show for the first time in Primula the independence of pollen size from male incompatibility, and that pollen size is under gametophytic control, dominance for this character being controlled by a recombinable locus. We also confirm earlier suggestions that style length, stigma papilla length and style cell length are developmentally correlated, and are controlled by at least two loci with additive effects, that genes controlling male and female compatibility are recombinable, and that a recessive lethal gene is linked to the thrum chromosome.