652 Mutations 



nodes may adjust themselves to the forces which 

 tend to cause their expansion is by straighten- 

 ing the rope. In doing so they may find the re- 

 quired space, by growing out in an unusual 

 direction, bending their axes and twisting the 

 ribs. 



To prove the validity of this explanation, a 

 simple experiment may be given. If the fibro- 

 vascular rope is the mechanical impedimeni 

 which hinders the normal growth, we may tr^ 

 the effect of cutting through this rope. By this 

 means the hindrance may at least locally 

 be removed. Now, of course, the operatior 

 must be made in an early stage before 

 or at the beginning of the period of growth 

 in every case before the uncurling of th( 

 rope begins. Wounds made at this time are ap1 

 to give rise to malformations, but notwithstand 

 ing this difficulty I have succeeded in giving th( 

 necessary proof. Stems operated upon become 

 straight where the rope is cut through, thougl 

 above and under the wounded part they go oi 

 twisting in the usual way. 



Sometimes the plants themselves succeed ii 

 tearing the rope asunder, and long straight in 

 ternodes divide the twisted stems in two or mor( 

 parts in a very striking manner. A line of ton 

 leaf-bases connects the two parts of the serev 

 and gives testimony of what has passed withii 



