20 NEW ZEALAND NATURE-STUDY BOOK 
In the Barberry the spines are branched, and give rise in 
their axils to branches. Moreover, on the Barberry tree 
the whole of the transition stages between the leaves and 
spines can be traced. The spines of the barberry are 
modified leaves. 
In the common Furze, or Gorse, some of the thorns possess 
axilliary buds, and hence may be regarded as modified 
leaves ; whilst others are found on the ends of the 
stems. The stem, we have seen, never ends in a leaf, but 
in a bud which develops into a shoot ; hence when we find 
the stem terminating in a spine, we may regard the spine 
as a modified branch. Thus, in this plant, both leaves and 
branches have been modified to form spines. 
Prickles, or Outgrowths of the Bark. ‘The 
leaves and stems of Brambles and Roses have prickles 
or woody hooks growing out of them—well seen in 
the Blackberry and Bush-lawyer. These occur on the 
plant without any definite plan of arrangement. They do 
not arise in the axils of leaves, nor do leaves arise in their 
axils; they are, moreover, attached to the bark only, 
and may be easily torn off. For these reasons we may 
conclude that they are merely out-growths of the bark. 
It will be noticed that the so-called thorns on Roses and 
Brambles are wedge-like in shape, with a 
narrow elongated base, and -grow on the 
stem in such a position that they are easily 
removed if pressed sideways, but offer con- 
siderable resistance to a force applied in the 
direction of their greatest length. Since the 
opposing force of the support acts in this 
direction, the importance of their position 
and arrangement is at once manifest. 
Fig, 21. 
Prickles on Plants armed for Defence. The green 
tem of 
RRAtnbIé. leaves and the fruit of plants furnish food 
