8i5 



the bending of the branch^ The loosening of the tissue, manifested at the 

 bend, can no longer be recognized on the upper side. On the other hand, 

 on the under side it may be traced for 6 cm. toward the tip. 



The wood cells are the widest at the bend but are wider above it than 

 below it; they seem to be wider on the under side of the branch than on the 

 upper side. 



The anatomical changes vary in c^uantity according to the size of the 

 curve, which the twig describes when bent, as well as the time of bending, 

 the species and, indeed, the individuality of the branch. 



Therefore, one has in the bending of branches a simple means for mod- 

 erating the grozvth in length and for directing the supply of water tozvard 

 the buds which, because of their position and nature, are capable of little 

 further development. 



The Twisting 

 OF Branches 



The effect of twisting 

 the branches is much more 

 pronounced and persistent 

 than that of bending, but 

 follows the same general 

 principles. It represents a 

 further cultural method for 

 the fruit grower, wdien he 

 wishes to change the growth 

 of branches. During the 

 period of growth, a too lux- 

 uriantly growing branch is 

 first loosened in a short 

 woody region by a half turn 



of the tissues about their long axis ; hereby the tissue is usually crushed and 

 split longitudinally and then bent at this broken place, with the tip of the 

 branch downward, so that the tip is permanently bent toward the base. Thus 

 at the place of twisting the under side of the branch lies on top ; the former 

 upper side forms the inner side of the sharp bend, in which the wood is 

 broken down to the pith. 



The most comprehensive view possible of the changes produced by 

 twisting is given in the longitudinal section through the knotty, deformed 

 place of twisting, which is a year old (Fig. 195). In this figure, m indicates 

 the pith which has been destroyed by the breaking of the wood when 

 twisted ; h is the wood of the present upper side on which a bud is seen at a. 

 Because of the turning of the under side to the present upper side, the wood 



1 On the production of tension due to pressure, compare Ursprung:, H., Beitrag- 

 zur Erklarung des exzentrischen Dickenwachstums an Krautpflanzen. Ber. d. 

 Deutsch. Bot. Ges. 1906, Part 9, p. 499. Further: Blicher, H., Anatomische Veran- 

 derungen bei gewaltsamer Krummung- und g-eotropischer Induktion. Jahrb f. 

 Wiss. Bot. 1906, Vol. 43, p. 271. 



Fig. 195. A branch bent with its tip downward 



and twisted at the point of bending about its 



longitudinal axis, after the coalescence of the 



inner injuries. 



