large numbers in the study of Mendelism, and recent stud- 

 ies reveal the fact that many cases of Blended and Mosaic 

 Inheritances also act according to Mendelian laws. Ex- 

 amples of these are given in the Chapter on Mendelism. 



Chapter 14.— HYBRIDS AND HYBRIDIZATION 



Hybrids in the modern sense are the product of crosses 

 between individuals belonging to different races or elemen- 

 tary species. Such races or species may belong to differ- 

 ent Linnsean genera, species or varieties. But it is not 

 possible to produce hybrids from any two races of plants or 

 animals taken at random, and systematic relationship is not 

 always a reliable guide to capacity for hybridization. This 

 capacity is usually restricted to nearly related plants and 

 animals. As a rule, the closer the alliance is, the greater is 

 the capacity for crossing. Experiments go to show that 

 crosses between species are not rare, as for example, brown 

 and polar bear, horse and zebra, horse and ass, cow and 

 bison, duck and goose, canary and finch, pheasant and 

 fowl, thrush and blackbird, raspberry and blackberry, 

 wheat and rye, species of strawberry, etc. 



The development of our knowledge of hybridization is 

 largely due to Koelreuter (1733-1806), Knight (1758-1843), 

 Gaertner and Darwin. Later additions to our knowledge 

 were contributed by Naudin, Focke, Vilmorin, Mendel, 

 DeVries and many others. Fairchild, an Englishman, was 

 the first gardener to raise a hybrid, in 1817, by pollinating 

 the stigma of Dianthus caryophyllus with pollen from 

 D. barbatus. Koelreuter was the first botanist to carry on 

 experiments on hybridization on a large scale for years. 

 His first hybrid, Nicotiana rustica x N. paniculata was pro- 

 duced in 1761. He made an important discovery in plant 

 breeding, that the product of reciprocal crosses are identi- 

 cal. Moreover, he established on a firm basis the theory of 

 sexuality of plants. 



Thomas Andrew Knight produced several commercial 

 varieties by crossing and has been called the father of 

 modern plant breeding. He enunciated two important 

 principles, viz. (1) food supply is the main cause of varia- 

 tion, and (2) crosses are often more vigorous than the 

 parents. 



Carl Friedrich Gaertner, son of Joseph Gaertner a dis- 

 tinguished botanist, carried out a very large number of ex- 

 periments (nearly 10,000) in crossing, and the results were 



