264 THE POPULAR SCIENCE MONTHLY 



ANOTHEE MODE OF SPECIES FOEMING 1 



Br LUTHER BURBANK, 



SANTA BOSA, CAL. 



THE more usual concept of the formation of species is by slow varia- 

 tions so well known as the Darwinian theory, which though 

 attacked from every point, still is and must always in the main be 

 accepted, for without question it gives the fundamental principles of 

 evolution as had never been done before. Yet the boundless amount 

 of research along these lines during the last half century has developed 

 strong new sidelights which illuminate, and in some cases compel a 

 slightly different view of, some of the suggestions of the master, Darwin. 



During the period of forty years that I have been experimenting 

 with plant life both in bleak New England and in sunny California, ex- 

 tensively operating on much more than four thousand five hundred 

 distinct species of plants, including all known economic and orna- 

 mental plant forms which are grown in the open air in temperate and 

 semi-tropic climates, as well as many of those commonly grown in 

 greenhouses and numerous absolutely new ones not before domesticated 

 and on a scale never before attempted by any individual or body of 

 individuals, numerous general principles have pressed themselves for- 

 ward for discussion and observation. Only one of these can be dis- 

 cussed at this time, and this briefly, more as a text for further observa- 

 tions and experiments than as anything like a full view of this highly 

 interesting mode of species formation. 



In the first place, let me say that our so-called species are only 

 tentative bundles of plants, no two individuals of which are exactly 

 alike, but nearly all of which quite closely resemble each other in gen- 

 eral outside appearances and in hereditary tendencies. Yet no one 

 can tell just what the result will be when combinations of these in- 

 herent tendencies are crossed or subjected to any other disturbing fac- 

 tor or factors. Like the chemist who has new elements to work with, 

 we may predict with some degree of accuracy what the general results 

 will be, but any definite knowledge of the results of these combinations 

 is far more difficult, even impossible, as the life forces of plants and 

 animals act in infinitely more new directions than can any ordinary 

 number of combinations of chemicals. 



Only a few years ago, it was generally supposed that by crossing 

 two somewhat different species or varieties a mongrel might be pro- 

 duced which might, or more likely might not, surpass its parents. 



1 Read at the annual meeting of the American Breeders' Association, at 

 Columbia, Mo., January 5 to 8, 1909. 



