438 GENETICS IN RELATION TO AGRICULTURE 
T. porrifolius) which bloomed in 1759, was, according to Focke, the 
first plant hybrid to be produced for scientific purposes. But Linnaeus’ 
ideas as to the possibility of hybrids between even widely different an- 
cestors were somewhat fantastic. 
Meanwhile, another investigator had been laboring on many fruitless 
experiments. Joseph Gottlieb Koelreuter laid the foundation for the 
modern study of hybridization in plants. It was not until 1760 that he 
obtained seeds from a cross between two species of tobacco (Nicotiana 
rustica 9 X N. paniculata # ). The hybrid plants bloomed in 1761 and 
the same year appeared his paper on sexuality in plants. He called 
attention to the rédle of insects in cross-pollination and estimated the 
number of pollen grains. According to Focke, but little interest was 
taken in his work by others as he was decades ahead of his time. He 
accumulated data of the greatest significance on the characters of inter- 
specific hybrids. Besides Nicotiana, he worked with several species of 
Dianthus, Aquilegia, Matthiola, Melandrium, Linum, Malva, Lavatera, 
Lobelia, Datura, Lycium, Verbascum and Digitalis. 
Toward the close of the 18th and during the first half of the 19th 
century this work of Koelreuter was extended in some directions by 
other scientists, notably by Duchesne, Sprengel, Herbert and Gaertner. 
Duchesne introduced the idea of races into botany and thus helped in 
breaking down the Linnaean dogma of the constancy of species. Sprengel 
studied the relations between flowers and insects in great detail. Herbert 
interested himself in a long series of experiments with species of Erica, 
Gladiolus, Hippeastrum and Rhododendron, securing many interesting 
results. He also engaged in a discussion with Knight on fertility in 
interspecific hybrids. Focke considers this debate in the nature of an 
introduction to the later more comprehensive controversy between 
Cuvier and Geoffrey St. Hilaire. Gaertner’s experimental work extended 
over several decades and in number of experiments probably he is sur- 
passed by no other hybridizer, but unfortunately his records and dis- 
cussions of results are clumsily reported and, according to Focke, their 
worth is frequently overestimated. His investigation of fertilization 
was of greater value. 
During the last half of the 19th century the scientific knowledge 
of plant hybrids was extended by a number of other investigators whose 
contributions have been thoroughly reviewed by Focke. Especially 
significant for agriculture was the work of Godron, Naudin, NAgeli, 
Darwin and Mendel. Godron, by hybridization of wheat and spelt, 
demonstrated the hybrid origin of Aegilops trit/cotdes and so destroyed 
the old tradition that spelt had been transformed into wheat. Naudin 
opposed the conception, still maintained by Cuvier, that species are hard 
and fast entities and, based on his experiments in hybridizing different 
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