I] 



TWISTING OF PETIOLES 



11 



branches of the Silver Fir, the Yew, Chestnut, Box, Hazel, 

 Diervilla, and many other plants, we find the leaves 



Fig. 2. Lateral horizontal shoot of Acer platanoides, Norway Maple, 

 viewed from above and showing the arrangement and display of the 

 leaves (K). 



apparently arranged in a distichous manner, right and left 

 on the branch, or in lateral series, as if combed to each 

 side, though closer inspection shows that their phyllo- 

 taxy is quite different, and that the change in display is 

 due to twistings of the petioles (Fig. 3). 



Similar twistings are concerned in the disposition of 

 the leaves of the Ivy, Ficus repens, and other plants which 

 climb up walls, and those of prostrate plants, such as 

 Helianthemum, Satin; repens, Lysimachia nemorum and 



