LUTHER BURBANK 



Sir Almroth Wright's inoculation for the preven- 

 tion of typhoid fever. It is at least within the pos- 

 sibilities that a not dissimilar inoculation may give 

 the tree immunity by developing its powers of re- 

 sistance, quite as the human sxibject is given 

 immunitj'. 



Of course the tree has no arterial system that 

 can be inoculated with hypodermic syringe as the 

 human subject is inoculated. But tHe life of the 

 tree is dependent on the circulation of fluids with- 

 in its tissues none the less. These fluids are taken 

 in by the roots, and they find their way to the ut- 

 termost leaf. So it is conceivable that by proper 

 treatment of the soil about the tree, the tissues of 

 the tree itself might be so altered as to become 

 resistant to the attacks of the bacterial enemies. 

 Immunity Through Treatment and Breeding 



Nor is this idea altogether theoretical. Experi- 

 ments have already been made that look to the 

 checking of the growth of the tree by withholding 

 fertilizers and water, that the development of the 

 tender buds and shoots, which are the usual points 

 of attack of the enemy, may be made to take place 

 slowly and thus to present tissue of a less succu- 

 lent order. 



Such hardening of the wood by withholding 

 water has proved effective in the case of some pear 

 orchards in Colorado, where it appears that the 



[132] 



