LUTHER BURBANK 



trait, is able to reassert itself in a certain number 

 of the offspring of the second filial generation, 

 causing these to "throw back" to their dwarfed 

 ancestors in the fullest measure. 



The capacity for large growth has been abso- 

 lutely left out of their individual make-up. 



In the Mendelian phrase they are pure reces- 

 sives; or, using the more technical terminology, 

 thej"^ are "homozygous" as to the hereditary 

 factors or determiners of the unit character of 

 dwarfness. 



The reader may or may not feel that the new 

 terminology adds to our comprehension of the 

 phenomena. But in either case the fact of the 

 appearance of the dwarf specimens of the second 

 generation among the hybrids is at least in a 

 sense explained by our knowledge that there were 

 dwarfs in their ancestry. 



How Account for the Giants? 



But while we are thus supplied with a more 

 or less satisfactory explanation of the appearance 

 of the dwarf hybrids, the colossal companions of 

 the same generation are as yet unaccounted for. 



It is a familiar fact, as just pointed out, that 

 hybrids of different species do tend to take on 

 new capacities for growth. But what hereditary 

 warrant have the upstarts for thus out-doing 



[160] 



