Hybridization 125 



fertilized with their own pollen are either absolutely or in 

 some degree sterile ; if fertilized with pollen from another 

 flower on the same plant, they are sometimes, though 

 rarely, a little more fertile ; if fertilized with pollen from 

 another individual or variety of the same species, they 

 are fully fertile ; but if with pollen from a distinct species, 

 they are sterile in all possible degrees, until utter sterility 

 is reached. We thus have a long series with absolute 

 sterility at the two ends; at one end due to the sexual 

 elements not having been sufficiently differentiated, and 

 at the other end to their having been differentiated in too 

 great a degree, or in some peculiar manner." 



Difficulties in making successful crosses. The diffi- 

 culties in the way of successful results through hybridiza- 

 tion are, therefore, these : the difficulty of effecting the 

 cross, infertility, instability, variability, and often weak- 

 ness and monstrosity of the hybrids; and the general 

 impossibility in most cases of predicting results. The 

 advantage to be derived from a successful hybridization 

 is the securing of a new variety which shall combine in 

 some measure the most desirable features of both parents ; 

 and this advantage is often of so great moment that it is 

 worth while to make repeated efforts and to overlook 

 numerous failures. 



Hybridization and asexual propagation. Among the 

 various characters of hybrid offspring, probably the most 

 prejudicial one is their instability, their tendency to vary 

 into new forms or to return to one or the other parent 

 in succeeding generations. At the outset, we notice that 

 this discouraging feature is manifested chiefly through 

 the fact of seed-reproduction, and we thereby come 



