Karl Friedrich von Gaertner was a well-known German botanist, and the son of Joseph Gaertner. He was a pioneer in the study of hybrids, and he is considered an important influence on Gregor Mendel.
Gärtner, who was a protestant, challenged the doctrine of Carl Linnaeus of the "new special creation" which stated that new species of vegetation could arise through hybridization. He defended the stability of species, and argued that although the transmutation of species was evidently possible, the new species would not last because of a law of reversion which prevented them from spreading freely. As was reported in the words of Mendel:
Gärtner by the results of [his] transformation experiments, was led to oppose the opinion of those naturalists who dispute the stability of plant species and believe in a continuous evolution of vegetation. He perceives in the complete transformation of one species into another an indubitable proof that species are fixed within limits beyond which they cannot change.