AUSTRAL-AMERICAN REGIONS. 



131 



5. The Chilian mountain-region, on the slope of the Andes. 



■Returning to the 20tli of April ; to our party on horseback ascend- 

 ing among hills and ridges a wide mountain-valley of the Andes, 

 devoid of fearful precipices and deep ravines. We at length emerged 

 from the hills, as the bottom of the valley became more even ; the 

 columnar Cereus having disappeared, together with the Myrtaceae and 

 all large shrubs, and grasses even becoming rare. Ever since leaving 

 the coast, the climate had been increasing in aridity; the increase 

 being now more decided, at the end of some six miles from the car- 

 riage-road, and at the estimated elevation of about six thousand feet, 

 we entered a new botanical region ; marked by the Chiiquiraga sud- 

 denly making its appearance. 



The vegetable growth soon entirely changed in character; becoming 

 much denser, very uniformly from one to two feet high, and composed 

 principally of spinescent plants: more generally spinescent than in 

 Patagonia, and unaccompanied by any tendency in the leaves to become 

 diminutive. The spinescent plants consisted of the Ghuquimga, every- 

 where conspicuous : and intermingled more or less abundantly, the 

 Berheris empetrifolia ; a second species of Berberis, somewhat rare ; 

 gen. Nassauv., having entire sharp-pointed leaves; gen. Rosac? with 

 fasciculate leaves, rigid linear and pointed; MiiUnum spinosum, closely 

 resembling the Patagonian species, and exceedingly abundant; gen. 

 Legum., imitating the last-named plant in its divided spinescent phyl- 

 lodia ; and the Pentaphorus, now much stunted, with tapering rigid 

 twigs. The prevailing habit of growth extended even to a species 

 of Verbena; which, though scarcely more than herbaceous, put forth 

 abortive branchlets, pointing in various directions like long green 

 spines. 



Other plants, not spinescent, yet well harmonizing with the above 

 in their rigid and branchy stunted habit, were intermingled : as gen. 

 Legum. with linear leaflets; several Aplopappi ; a Baccharis; two 

 Liatroid shrubs; and the Ephedra, now depressed to the prevailing 

 average stature. A few species, however, refused to conform ; their 

 fresh, unmodified aspect and foliage seeming out of place : as, an orna- 

 mental SoJanum, having lanceolate and somewhat coriaceous leaves ; 

 and especially, two or three yellow-flowered Senecios with dark-green 

 foliage. 



