THE CACTUS 123 



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 

 utilized numbered scores of alleged species, be- 

 tween 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 ex- 

 pansive scale that was contemplated. 



The seeds from different crosses were planted 

 separately, and the character of the seedlings 

 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 with- 

 out spines, for it is a familiar doctrine that the 

 developing embryo reproduces in epitome the 

 stages of its racial history; and the plant at the 

 cotyledon stage may be regarded as really still 

 an embryo, inasmuch as it is drawing its nourish- 

 ment from the nutritive matter stored in the 

 seed. 



