I. Variation in Floral Construction, Breeding System Correlates, and Their Possible Evolutionary Significance in Crataegus sect.
Polyploidy is associated with apospory, self-fertility, and varying degrees of pollen sterility.
Variation in stamen number may also be correlated with variation in distribution, phenology, leaf shape, and other features of floral morphology, leading to recognition of taxa at the specific or infraspecific level. Comparable variation in stamen number is virtually unknown in Eurasian hawthorns, as in the majority of flowering plants. These data on breeding system and morphological variation may be explainable in terms of hypotheses linking gametophytic apomixis, polyploidization, and optimal strategies for pollen dispersal. Text Institute of Botany, Academy of Sciences of the Czech Republic, 1996.