288 GENETICS IN RELATION TO AGRICULTURE 
1768 nearly 2000 sorts were known in Holland. But in 1864 only 700 
varieties were found in the largest garden in Haarlem, which fact in- 
dicates a gradual process of elimination of the less desirable selections 
of earlier years. 
Pioneers in Plant Breeding.—The systematic breeding of crop plants 
was begun in Europe during the latter part of the 18th century. Jean 
Baptiste Van Mons, a Belgian physician and professor of physics and 
chemistry in the University of Louvain, pursued plant breeding work as 
an avocation. But so great was his zeal in an effort to demonstrate 
certain theoretical ideas which he held concerning the improvement 
of fruits that the results of his labor were extensive. His experiments 
were begun in 1785. Thirty-eight years later he had 80,000 seedling 
trees in his ‘“‘ Nursery of Fidelity,” as he called it, at Louvain. He dis- 
tributed cions without charge to many countries including America. 
He specialized on pears and his first catalogue, issued in 1823, lists 
1050 varieties. Altogether he originated nearly half that number. 
Van Mons’ service to agriculture, especially to pomology, has been 
widely recognized.! 
Three other pioneer breeders who began their work during Van 
Mons’ life are Thaer, Knight, and Cooper, representing Germany, Eng- 
land, and the United States respectively. During the latter portion of 
the 18th and the earlier years of the 19th centuries each of these men 
carried on experiments in plant breeding and made contributions of 
tremendous importance to agriculture. Thomas Andrew Knight was the 
first to show the value of hybridization in plant improvement. Accord- 
ing to Bailey, in the variety, accuracy, significance, and candor of his 
experiments, Knight stands to the present day without a rival among 
horticulturists. He was also a successful breeder of livestock and author 
of papers on plant physiology and breeding. Albrecht Daniel Thaer 
also made hybridizing experiments but ernmphasized the value of selection. 
Plant breeding was only one of his many agricultural interests and he is 
credited with having laid the foundation of scientific agriculture of 
today. Joseph Cooper disproved the current fallacy as to the entire 
necessity for changing seed and showed the American farmer the impor- 
tance “‘of selecting seeds and roots for planting or sowing, from such vege- 
tables as come to the greatest perfection, in the soil which he cultivates.” 
Like Van Mons, each of these men had his theories, but only experience 
revealed the truth in those theories. Based on their experience they 
formulated certain rules which they knew would yield results, but fre- 
quently the conclusions reached by them were only partially true. 
At least five other men deserve to be mentioned among the earlier 
1 For a discussion of Van Mons’ theories and contributions (also of the work of 
Knight and Cooper) see Baiuny, L. H.: “Survival of the Unlike,” 1906, pp. 141-159. 
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