LUTHER BURBANK 



produced were hybridized, when my more exten- 

 sive experiments were under way, with the best 

 examples of the large Opuntias received from 

 all parts of the world. 



In making these crosses I bore in mind always 

 the condition of relative spinelessness, but also the 

 characteristics of the plant as regards size and 

 fruit-production and quality. 



The precise parentage of the hybrids of the first 

 generation was recorded, as already stated. But 

 when the seedlings came to be handled by literal 

 millions, and when the specimens that were util- 

 ized numbered scores of alleged species, between 

 which it was often difficult to differentiate, it 

 finally became impossible to attempt to follow the 

 exact pedigrees of the selected plants, if my 

 experiments were to be carried out on the 

 expansive scale that was contemplated. 



The seeds from different crosses were planted 

 separately, and the character of the seedling would 

 reveal at an early period the quality of the plant 

 as regards the tendency to produce spines, but not 

 at this early stage the quality or quantity of fruit. 



When the cactus seedlings first appear above 

 ground, their cotyledons are spineless. This sug- 

 gests a period when all cactus plants were without 

 spines, for it is a familiar doctrine that the devel- 

 oping embryo reproduces in epitome the stages of 



[202] 



