THE TREATMENT OF THE SHOOT 157 



change which the tissues undergo at the bend, and must, there- 

 fore, show itself also when branches which naturally grow in a 

 downward direction are bent upwards. 



(&.) The Twistitig of Shoots. 



The twisting of shoots acts in the same way, but much more 

 energetically. In this case the shoot is twisted half-way round 

 during its period of growth and while still in its normal position. 

 By so doing the woody portion in which the twisting takes 

 place is loosened, and probably split up in the interior. After- 

 wards the shoot is also bent permanently downwards at this 

 point, so that the shoot forms a loop with the tip of the 

 shoot pointing downwards. At the bend the under surface of 

 the twig comes to lie above, and the wood is split up into a 

 number of spirally twisted loops. 



The region at which the twisting takes place forms a con- 

 siderable swelling, in which, as is revealed by the microscope, a 

 formation of parenchymatous tissue has filled up the splits. The 

 cambium, too, has gradually re-formed into a continuous ring, 

 producing new wave-like masses of wood round the broken 

 tissues. 



The breaking up of the woody tissues and the twisting 

 the more delicate bast necessitates of course the loss of the 

 upper portion of the branch, and all that is effected is a dimi- 

 nution of the upward passage of water and a supplying of the 

 buds immediately above the bend with the assimilated mate- 

 rial which continues to be formed in the upper leaves of the 

 shoot. 



In layering quinces, the shoots are often twisted about their 

 long axis at the point at which the roots are to be formed. 

 The plastic material passing down from the leaves accumulates 

 at the twist, and can be used for the production of adventitious 

 roots. 



In the Caucasus it is usual to twist the fruit-stalks of the 

 ripe grapes, so as to produce an especially good sort of wine. 

 The explanation of this procedure lies in the fact that the 

 supply of water to the grape is diminished, while the evapora- 

 tion from the berries remains the same ; consequently, the sugar- 



