Koelreuter
was a plant hybridizer.
Between 1760 and 1766 he carried out the first
series of systematic experiments in plant
hybridization ever undertaken (Nicotiana paniculata x
N. rustica). He found that the hybrid offspring
generally resembled the pollen parent as closely as
the parent upon which the seed was borne. Thus for the
first time it was found that the pollen grain has an
important part in determining the characters of the
offspring. This was a novel idea and disbelieved by
his contemporaries. He also observed accurately the
different ways in which the pollen can be naturally
conveyed to the stigma of the flower. He discovered
the function of nectar and the part played by insects
and by wind in flower pollination. He also observed
that hybrid plants often exceed their parents in vigor
of growth.
