16 The Principles of Fruit-growing 



holes necessary to give satisfactory information as to the 

 character of the underlying strata will vary. If it be found 

 that half a dozen holes dug in a certain 5- or 10-acre tract 

 give practically the same result in each case, it may usually 

 be assumed that these indicate the general character of 

 the subsoil. If, on the other hand, the verdict is variable) 

 more holes will have to be dug imtil the limits of the differ- 

 ent formations are shown. Where neither rocks nor stones 

 are present, this work may be done more quickly and quite 

 as satisfactorily with a ground-auger as with a spade. A 

 home-made auger is usually quite as satisfactory for this 

 purpose as the more expensive article purchased on the 

 market. Take an old IJ^- or 2-inch wood-auger and have 

 the local blacksmith weld it to the end of a 6-foot length 

 of ^-inch pipe or 3^-inch wrought iron rod. The welding 

 of a short cross-piece at the top completes the device. 



^An open porous subsoil insures drainage and thus pro- 

 motes the establishment of deep feeding roots.) Trees with 

 such root-systems are not subj ect to the vicissitudes of vary- 

 ing seasons to the same extent as those of a shallower root- 

 system. . . _. The capacity to penetrate impervious 

 subsoils does not depend on the boring power of the root- 

 tip. All roots have a boring power which is quite sufficient 

 to force their way down in any ordinary subsoil. The rea- 

 son for the absence of roots is that they are unable to live 

 in the denser soil, owing to the lack of the necessary air. 

 Thus it will be found that a soft mucky subsoil is quite as 

 efficient a barrier to root-growth as solid rock." 



The parasite determinant. 



Inasmuch as many of the organisms that seriously in- 

 terfere with fruit-growing are more or less restricted in 

 their range, it would seem to follow that the zones of profit- 



