218 INBREEDING AND OUTBREEDING 



by seed propagation, would be a comparatively easy 

 undertaking. 



With plants which are propagated vegetatively, the 

 matter is even less difficult. Nearly all varieties of fruits, 

 flowers and vegetables propagated in this way are notori- 

 ously unstable when grown from seed. The excellent 

 varieties that we now have undoubtedly owe their supe- 

 riority in large measure to a fortunate combination of 

 many different characters so made as to obtain the maxi- 

 mum effect from hybrid vigor. Attempting to obtain 

 further improvement by crossing these already widely 

 crossed varieties is like trying to solve a picture puzzle 

 in the dark. First analyze the material to be used by 

 systematic and rigorous inbreeding, let the consequences 

 be what they may. Then cross the different constant 

 types which may be ultimately obtained and test one com- 

 bination after another until a real improvement is effected. 

 When that is done the individuals can be propagated in- 

 definitely by the same means utilized before. Of course, 

 this method has the objection that many of the plants 

 propagated asexually require several years for each 

 sexual generation. Results would be slow for that reason, 

 it is true, but thev would be sure. 



v 



With animals the application of this method would be 

 quite a different proposition. Inbreeding closer than 

 brother and sister mating could not be practiced, and the 

 time required to obtain purity and constancy would be 

 much greater than is the case with self-fertilization. 

 Moreover, the number of individuals which could be ob- 

 tained would be so small that selection could not be made 

 advantageously. Finally, the cost of raising most ani- 

 mals is so great that the maintenance of animals of little 



