Figure 1.

Hybrids resulting from a cross between H. auricula × H. aurantiacum. H. auricula × H. aurantiacum was only one of many crossing combinations effectuated by Mendel, although it was the one with by far the largest progeny. Since Mendel, in preliminary experiments, ascertained that both parents were “true breeding,” he considered them to be “constant species.” But instead of an expected uniform F₁, he obtained, to his consternation, segregating offspring covering the whole palette of transitions, as illustrated here by a figure from Ostenfeld (1910), who repeated the same cross. Mendel could not have known at that time that the pollen parent H. aurantiacum is, in reality, a highly heterozygous hybrid, genetically fixed thanks only to apomictic reproduction, and thus feigning a true-breeding “species.”