LUTHER BURBANK 



hybrid's ancestry are kept constantly in mind, 

 serves to give us a clue to the observed tendency 

 of families or strains of animals or plants to 

 revert in successive generations toward a given 

 mean or average. 



It has long been observed that, as a general 

 rule, the offspring of human parents that are 

 exceptionally tall tend to be shorter than their 

 parents; whereas, contrariwise, the offspring of 

 dwarfs tend to be taller than their parents. 



In studying races of animals and plants, biol- 

 ogists have discovered that this tendency, spoken 

 of as tendency to revert to a mean, is universal. 



The matter has been especially studied in 

 recent years by the Danish biologist. Professor W. 

 L. Johannsen, of Copenhagen. His studies of 

 barley and of kidney-beans show that any given 

 race of these plants is really made up of a number 

 of subordinate races, representing different strains 

 of the ancestral pedigree, and that when the plants 

 are self-fertilized, the progeny tend to group them- 

 selves into a few more or less permanent types. 



There are limits of variation as to size, color 

 and qualities but the progeny as a whole do not 

 tend to have offspring that approach the half-way 

 mark between these two extremes. Rather they 

 break up into groups, each group tending to 

 reproduce itself in such a way as to form a new 



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