Xew York AcxBicultural Experiment Station. 8-il 



But within the past ten years plant breeding 



New laws of has made rapid advances, owing to the dis- 



breeding revealed covery, after it had lain hidden for half a 



century, of work which established some very 

 (Jementary laws of heredity. These laws make it possible to work 

 with plants, and, to quite an extent, with animals with a certainty 

 of securing the desired results with much less effort and time than 

 in former years. 



This old work of Johann Mendel established the fact that some 

 of the characters, of both plants and animals, are inherited un- 

 changed, passing down through each subsequent generation. 

 Many of them may be hidden in the first generation of progeny 

 and in a fraction of the descendants of each subsequent generation 

 by the " dominance " of stronger, opposed, or differing, character- 

 istics of the same group. But both the " dominant " and the " re- 

 cessive " (weaker or hidden) character of a Mendelian pair re- 

 appear in pure form in part of each generation after the first; 

 so that the descendants of two parents, both showing the same one 

 of these pure characters, will always be like their parents in re- 

 spect to this character. 



Now, the problem of the breeder is to ascertain what characters 

 follow this law — for not all do — and to secure the ones desired 

 in pure form and in suitable combinations. When once secured 

 as desired in two parents, the descendants may be depended on to 

 show the same characters and not to " revert " to some form not 

 wanted. But, even simplified as it is, the problem is still very 

 complex ; for the features or characteristics we think of as separat- 

 ing one plant or animal from another may each be made up of two 

 or more heritable characters ; and the possible combinations, in any 

 individual, of these varied " unit characters " are exceedingly 

 numerous and varied. All these variations must be secured and 

 checked by growing multitudes of seedlings, of at least two gener- 

 ations, before we can be positive of our ground on more than a few 

 characters. 



