242 Principles of Plant Culture. 
smaller branches together, to form a connection between 
them (Fig. 163). The branches thus twisted often grow 
together, forming a tie of great strength. A main branch 
that has actually commenced to split down may often be 
saved by passing an iron bolt through it and the remainder 
of the trunk. A bolt thus inserted may become entirely 
inclosed by later growth. _ 
Fic. 161. Unpruned apple tree, with head too dense to admit light. 
-B—STIMULATIVE PRUNING 
This depends upon the principle: the suppression of growth 
in one direction tends to stimulate it in others. Stimulative 
pruning may be employed either to stimulate growth of 
leaves, branches and roots, or of flower-buds. 
