24 DARWINISM chap. 



river sometimes rose 30 feet in eight hours, doing immense 

 destruction, and the abundance of the larger carnivora and 

 large reptiles on its banks, he goes on : " But it was among 

 the flora that the j>rinciple of natural selection was most 

 prominently displayed. In such a district — overrun with 

 rodents and escaped cattle, subject to floods that carried away 

 whole islands of botany, and especially to droughts that dried 

 up the lakes and almost the river itself — no ordinary plant 

 could live, even on this rich and watered alluvial debris. The 

 only plants that escaped the cattle were such as were either 

 poisonous, or thorny, or resinous, or indestructibly tough. 

 Hence we had only a great development of solanums, talas, 

 acacias, euphorbias, and laurels. The buttercup is replaced by 

 the little poisonous yellow oxalis with its viviparous buds ; the 

 passion-flowers, asclepiads, bignonias, convolvuluses, and climb- 

 ing leguminous plants escape both floods and cattle by climb- 

 ing the highest trees and towering overhead in a flood of 

 bloom. The ground plants are the portulacas, turneras, and 

 Oenotheras, bitter and ephemeral, on the bare rock, and almost 

 independent of any other moisture than the heavy dews. 

 The pontederias, alismas, and plantago, with grasses and 

 sedges, derive protection from the deep and brilliant pools ; 

 and though at first sight the ' monte ' doubtless impresses the 

 traveller as a scene of the wildest confusion and ruin, yet, on 

 closer examination, we found it far more remarkable as a 

 manifestation of harmony and law, and a striking example of 

 the marvellous power which plants, like animals, possess, of 

 adapting themselves to the local peculiarities of their habitat, 

 whether in the fertile shades of the luxuriant ' monte ' or on 

 the arid, parched-up plains of the treeless pampas." 



A curious example of the struggle between plants has 

 been communicated to me by Mr. John Ennis, a resident in 

 New Zealand. The English water-cress grows so luxuriantly 

 in that country as to completely choke up the rivers, 

 sometimes leading to disastrous floods, and necessitating great 

 outlay to keep the stream open. But a natural remedy has 

 now been found in planting willows on the banks. The 

 roots of these trees penetrate the bed of the stream in every 

 direction, and the water-cress, unable to obtain the requisite 

 amount of nourishment, gradually disappears. 



