134 NOTES OF A NATURALIST. 



the river, but several miles further north, and water is 

 doubtless conveyed there in some abundance, as, for 

 the first time since leaving Arica, a few bushes in 

 little enclosed gardens could be de^scried from the 

 harbour, and I was afterwards shown two stately 

 trees, the ornament of the place, which were nearly 

 fifteen feet in height. I went inland about a mile 

 and a half, visiting a slight eminence where the rock, 

 evidently very recent, crops out at the surface, and 

 one or two other promising spots. Most of the 

 country was covered with sand, in places soft and 

 deep, and anywhere else in the world I should have 

 thought it wretchedly barren, but after my recent 

 experience the meagre vegetation appeared almost 

 luxuriant. 



There is much interest attaching to the flora of this 

 desert region of South-western America. The species 

 which grow here are the more or less modified repre- 

 sentatives of plants which at some former period 

 existed under very different conditions of life. In 

 some of them the amount of modification has been 

 very slight, the species, it may be presumed, possess- 

 ing a considerable power of adaptation. Thus one 

 composite of the sun -flower family, which I found 

 here, and also at Payta, is but a slight variety of 

 Encelia canescens* which I had seen growing luxu- 

 riantly in the gravelly bed of the Rimac near Lima, 

 and along that river to a height of six thousand feet 



* The four species of Encelia described in De Candolle's " Pro- 

 dromus " appear to me to be but slightly modified forms of a single 

 species. Since the publication of that work, several other and quite 

 distinct species have been ranked under the same generic name. 



