Comparative Morphology of the Carpel in the Rosaceae. Iii. Pomoideae: Crataegus, Hesperomeles, Mespilus, Osteomeles

The carpels in Crataegus, Hesperomeles, Mespilus, and Osteomeles appear to constitute a morphologically related group: all have bony pits, ovules that tend to be acollateral (usually superposed), and clearly separate ovular and wing bundles, i.e., no “ventral” bundles, at the level of ovular insertion. In species whose carpels have no sutural opening, the integuments are more extensively fused with one another, the degree of intercarpellary fusion tends to be greater, and the carpels are fused with the floral cup to relatively higher levels than in those species whose carpels have a sutural opening. In the few cases in which wing and ovular bundles are adnate at the locular base ( Crataegus monogyna, Mespilus, Osteomeles anthyllidifolia, O. Schwerinae ), the extent of inter‐ and extracarpellary fusion and sutural closure is among the most advanced.