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IOWA ACADEMY OF SCIENCE Vor. XXIX, 1922 
THE SIGNIFICANCE OF SPRENGEL’S DISCOVERY TO PLANT 
BREEDING 
Christian Konrad Sprengel (1750-1816) published in 1793 an 
epoch-making book “The Newly Revealed Secret of Nature in the 
Structure and Fertilization of Flowers.” It was Sprengel’s chief 
contribution to discover the fact of insect pollination. His conclu- 
sion, that nature in most cases intended that flowers should not be 
fertilized by their own pollen and that the peculiarities of flower 
structure can be understood only when studied in relation to the 
insect world, was revolutionary for his time. 
The significance of Sprengel’s discovery to plant breeding lies 
in the fact that in general most flowering plants with definite 
floral envelopes are naturally cross-fertilized. It. means simply 
this, that the bringing together of new combinations of parental 
characters is the rule rather than the exception in nature, and that, 
therefore, the breeding of new types in the plant world may be said 
to be going on all the time. 
PRE-MENDELIAN BREEDERS OF THE NINETEENTH CENTURY 
At the beginning of the nineteenth century there began to ap- 
pear in England the first signs of the application of the science of 
hybridization to the practical art of breeding, in the work of 
Thomas Andrew Knight and William Herbert. 
Knight was a country gentlemen by occupation, born August 12, 
1759, and educated at Oxford. He early began to interest him- 
self, on his estate at Elton in Herefordshire, in experiments in 
the raising of new varieties of fruits and vegetables. In 1841, 
three years after his death, a collection of eighty-two of his papers 
was published by the botanists Bentham and Lindley. Knight’s 
principal work of crossing was carried out with currants, grapes, 
apples, pears, and peaches, to the end of producing hardier and 
superior fruits. One of his discoveries of genetic interest was 
that, in crosses of varieties of red upon white currant, by far the 
greater number of the hybrids' produced red fruit, i.e., the 
dominance of red. A conclusion formulated by Knight on the 
basis of his experience, and afterwards confirmed by Darwin, 
and since called the Knight-Darwin law, was that, “new varieties 
of every species of fruit will generally be better obtained by in- 
troducing the farina (pollen) of one variety of fruit into the 
blossom of another, than by propagating from one single kind. 
However, the work of Knight that attracts the most attention 
from the standpoint of genetics is his experiment with peas. The 
