XEROPHYTE SOCIETIES 
199 
trate or creeping habit is a much less exposed one in such 
regions than the erect habit. In the same manner, the very 
characteristic rosette habit, with its cluster of overlapping 
leaves close against the ground, tends to dimmish loss of 
water through transpiration. 
One of the most common results of xerophytic conditions 
upon body habit is the development of thorns and spiny 
FIG. 176. Young plants of Euphorbia splendens, showing a development of thorns 
characteristic of the plants of dry regions. 
processes. As a consequence, the vegetation of dry regions 
is characteristically spiny. In many cases these spiny pro- 
cesses can be made to develop into ordinary stems or leaves 
in the presence of more favorable water conditions. It is 
probable, therefore, that such structures represent reduc- 
tions in the growth of certain regions, caused by the unfavor- 
able conditions. Incidentally these thorns and spiny pro- 
cesses are probably of great service as a protection to plants 
in regions where vegetation is peculiarly exposed to the 
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