 "Tylosema esculentum" is heterostylous, meaning that two or three morphological types of flowers exist in the population.For this specific legume, its pistil and anthers show reciprocal heights in two morphological types.Experiments involving in vivo fertilization (naturally occurring crosses of living organisms) and in vitro fertilization (crosses done in a laboratory setting) indicated that a two-allele self-incompatibility system exists in "Tylosema esculentum."