646 Mutations 



nected with one another, constituting a ring 

 which narrowly surrounds the stem, and which 

 would impede an increase in thickness, if such 

 were in the nature of the plant. But since the 

 stems end their existence during the summer of 

 their development, this structure is of no real 

 harm. 



The grouping of the leaves in alternate pairs 

 may be seen within the bud as well as on the 

 adult stems. In order to do this, it is necessary 

 to make transverse sections through the heart 

 of the rosette of the leaves of the first year. 

 If cut through the base, the pair exhibit connate 

 wings, corresponding to the water-cups ; if cut 

 above these, the leaves seem to be free from one 

 another. 



In order to compare the position of leaves 

 of the twisted plants with this normal arrange- 

 ment, the best way is to make a corresponding 

 section through the heart of the rosette of the 

 first year. It is not necessary to make a micro- 

 scopic preparation. In the fall the changed dis- 

 position may at once be seen to affect the central 

 leaves of the group. All the rosettes of the 

 whole race commence with opposite leaves; 

 those that are to produce straight stems remain 

 in this condition, but the preparation for twist- 

 ing begins at the end of the first year as shown 

 by a special arrangement of the leaves. This 



