228 AN AMERICAN FARMER IN ENGLAND. 



CHAPTER XXXV. 



Decay of Varieties Two Theories : Knight's, Downing's English Theo- 

 ry and Practice Practical Deductions Causes of Decay Remedies 

 Hints to Orchardists Special Manures Pruning Thorough Drain- 

 ageA Satirical Sketch Shooting the Apple Tree. 



TT is known that many varieties of apples, which fifty years 

 * ago were held in high esteem as healthy, hardy sorts, bearing 

 abundantly very superior fruit, have now but a very poor repu- 

 tation, and varieties which a hundred years ago were very highly 

 valued and extensively cultivated, are now extinct. It is be- 

 lieved, too, that the most celebrated old varieties that are yet 

 cultivated, are much more subject to canker than others; or, 

 in other words, that trees of these varieties are more easily af- 

 fected by unfavorable circumstances, or have a more delicate con- 

 stitution. 



To account for this, there are two theories held by different 

 scientific horticulturists. The first which originated with the 

 late Mr. Knight, a distinguished vegetable physiologist of Eng- 

 land, who devoted much attention to the subject, and made a long 

 series of experiments upon it may be stated as follows : 



Each seedling tree has a natural limit to its life, and within 

 that will have a period of vigor, succeeded by a natural and in- 

 evitable decline, corresponding to the gradually incrasing feeble- 



