30 LUTHER BURBANK 



rough, but which are ''heterozygous" as regards 

 the unit characters under consideration, and 

 hence will show progeny of variously mixed 

 characteristics as to roughness or smoothness of 

 coat, and as to black or white color. 



This illustration, perhaps, gives as tangible 

 an impression as can well be gained of the 

 complexities that confront the experimenter 

 when he attempts to fix a new type of animal 

 or plant. 



I may state here that dominant characters in 

 any race are usually those more fixed in the past 

 by innumerable repetitions; generally ancient 

 and more fundamental characters. 



Even where only two unit characters are 

 involved, the progeny of the second generation, 

 as we have just seen, may break up into numer- 

 ous races, some fixed and others variable. And, 

 as we have previously pointed out, the compli- 

 cations thus introduced increase at a startling 

 ratio when more characters are under con- 

 sideration. 



Moreover, the matter is rendered increasingly 

 difficult for the plant experimenter by the fact 

 that he must often wait, particularly in the case 

 of orchard fruits, for a term of years before he 

 can know the result of any single breeding 

 experiment. To sort out the pure types from 



