652 Mutations 



nodes may adjust tliemselves 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 impediment 

 which hinders the normal growth, we may try 

 the effect of cutting through this rope. By this 

 means the hindrance may at least locally 

 be removed. Now, of course, the operation 

 must be made in an early stage before, 

 or at the beginning of the period of growth, 

 in every case before the uncurling of the 

 rope begins. Wounds made at this time are apt 

 to give rise to malformations, but notwithstand- 

 ing this difficulty I have succeeded in giving the 

 necessary proof. Stems operated upon become 

 straight where the rope is cut through, though 

 above and under the wounded part they go on 

 twisting in the usual way. 



Sometimes the plants themselves succeed in 

 tearing the rope asunder, and long straight in- 

 ternodes divide the twisted stems in two or more 

 parts in a very striking manner. A line of torn 

 leaf-bases connects the two parts of the screw 

 and gives testimony of what has passed within 



