IV] GEOTROPISM 49 



confine our attention to such cases as the Willows, where 

 the buds are appressed and point almost or quite ver- 

 tically, or to Spruce, Beech, &c. where the angle of 

 divergence is near 45°. 



When the young shoots emerge they come off at 

 angles not far from 45° with the vertical leader, and will 

 maintain that angle for many years as they thicken to 

 branches, often bending over at a wider angle later owing 

 to the weight of the foliage. 



But how is it that, while the buds and their shoots on 

 the main vertical axis of the leader thus point upwards, 

 at an acute angle with the vertical, those on the lateral 

 nearly horizontal shoots also point out at an acute angle 

 with the axis which bears them, and in many cases grow 

 out at such angles but in the horizontal plane ? 



The phenomenon is common enough. The buds and 

 shoots on the main stem of a Beech or Lime, for instance, 

 all point upwards, at acute angles not far from 45° with 

 the vertical axis above them : moreover, they are spirally 

 arranged on that axis. But the buds and shoots on the 

 overhanging and nearly horizontal lateral branches of the 

 same tree point outwards, at a similar angle with the 

 part of the axis bearing them but nearly in the hori- 

 zontal plane, approximating to the plane in which the 

 parent axis grows : moreover, these buds and shoots are 

 here not spirally arranged, but right and left on the axis 

 — i.e. distichous. 



Yet these distichous, horizontally directed shoots can 

 be made to develope spirally arranged and upwardly 

 directed buds and shoots by artificially fixing the parent 

 axis in the direction of the vertical. In other words, 

 by altering the position of the shoot-axis, we can 

 induce it to produce buds, leaves and shoots disposed 

 in a totally different manner from the normal to the 



w. V. 4 



