PLANT BREEDING 73 



de Vries and the modern school of experimenters, 

 stimulated by him either to support or controvert his 

 views and the original Darwinian conceptions, is the 

 introduction of the conception of the mutant. The 

 mutant is a new variety or species which arises suddenly 

 and not from a gradual series of inherited modifications, 

 and which breeds true. The best known example of 

 a species which has given rise to such mutations is the 

 Evening Primrose (Oenothera). Of the various species 

 of this plant literally tens of thousands of carefully 

 selected specimens have been bred by botanists all 

 over the world, and the several old established species 

 have yielded nearly a dozen of new, suddenly produced 

 forms, all of which ultimately " breed true," that is, 

 have offspring which, coming from seed, entirely 

 resemble the parents. 



The mutants of the Evening Primrose are not start- 

 lingly different from their original stock, but they are 

 constantly and recognisably different. Their produc- 

 tion at all is of great importance to the theories of 

 evolution, for since their recognition it has been possible 

 definitely to experiment and test this theory and the 

 many others which arise out it. 



At present the majority of plant breeders and muta- 

 tionists deal only with external characters, but a few 

 workers have begun to correlate these external changes 

 with the minute details of the cytology. It will be 

 remembered that in the chapter on cytology the im- 

 portance of the nucleus was emphasised, and we know 

 that all the characters that a plant inherits, whatever 

 they are, must have lain in one stage in one of the two 

 fusing gametes. A great field of experimental and 

 theoretic work lies in the future in the correlation of 

 the internal and external features in hybrids and in 

 the so-called mutants. 



