XV A CRITIC OF NATURAL SELECTION ANSWERED 311 



the same way, our holly, when it grows to a large size, 

 usually has the leaves towards the top spineless : the wild 

 pear also is spiny below but unarmed above. The climb- 

 ing palms, on the other hand, are armed to the very top, 

 but in this case the spines assist climbing. 



The anomaly of the flora of the Brazilian Campos, having 

 many of the true xerophiloas characteristics yet being 

 almost wholly without spiny forms, is quite in harmony 

 with the fact of the great poverty of this region in 

 mammals destructive of woody vegetation. There are 

 really none but a few deer and cavies, which are mostly 

 inhabitants of the more thickly wooded valleys, and which 

 are kept from undue multiplication by the considerable 

 number of species of Felida^ and Canidse in the same area. 



We are, therefore, led to conclude that the apparent 

 direct dependence of an unusually spinescent vegetation 

 on arid conditions of soil or climate is to a great extent 

 deceptive. Such conditions are inimical to the growth of 

 dense forest, and it is a well-known fact that the larger 

 mammalia abound most in partially wooded or open 

 country. Many of these animals are exceedingly destruc- 

 tive to shrubby or arborescent vegetation, especially in 

 districts which are subject to occasional droughts; and it 

 is in such areas that so many of these plants have acquired 

 the protective armature of spines or prickles, while others 

 not so protected have sooner or later succumbed, thus 

 leading to a preponderance of the former. But the 

 numerous instances in which considerable areas and 

 extensive floras are found to have hardly any spinous 

 plants, as compared with other areas in which the soil and 

 climate are generally similar and where such plants 

 abound — the only important difference being the absence 

 or presence of destructive herbivorous or frugivorous 

 mammals — show us clearly that it is the latter rather than 

 the former condition which is the real starting point and 

 efficient cause for the development of spines, while the 

 mode of their production has been through spontaneous 

 variation and Natural Selection.^ 



1 Professor A. Kerner gives an admirable account of the various 

 forms of spiny and prickly plants, which are exceedingl}' numerous in 



