CH. VIl] 



YEW BUDS. 



181 



of the leaves on the adult horizontal "branches is normally 

 and regularly produced by torsion of the internodes. In 

 the snowberry (Symphoricarpus) the difference between 

 the vertical and horizontal branches is especially easily 

 seen, as there are always plenty of vertical shoots springing 

 up round the shrub. In these the decussate arrangement 

 of the leaves is obvious, whereas in the horizontal shoots 

 the decussation is only visible in the quite young leaves, 

 the older ones are arranged in two horizontal ranks by 



Fig. 38. Exp. 225. Copied from Frank (loc. cit.). 



torsion of the internodes. Fig. 38 shows the torsion in a 

 horizontal shoot of a Lonicera. 



(226) The huds of the yew. 



In the young leaf-bud of the yew it will be seen that 

 the morphologically upper surfaces of all the leaves are 

 directed towards the centre. Since the shoot grows 

 horizontally it is clear that the leaves growing on its 

 upper surface must twist on their petioles in order that 



