72 DISTRIBUTION OF PLANTS. 



chiefly of small pebbles, as smooth as though sea-worn ; some of them 

 porphyritic, and a few quartzose ; and for the most part, derived evi- 

 dently from a distance. 



The country is usually termed " a Desert ;" but in place of the soil 

 remaining bare, the plants seem to have been adapted by extreme 

 structural modification to resist intense and long-continued drought. 

 Besides roots deeply penetrating, the twigs or branchlets of the shrubs 

 are very generally spinescent, bearing hard coriaceous foliage ; with a 

 tendency in the leaves to become diminutive, not witnessed in any 

 other part of the Globe I have visited. 



All over the country, scattered bushes were in general frequent, 

 eight feet in extreme height, and always growing isolated ; branching 

 from the base, and with a general stunted aspect, presenting all around 

 rigid, dense, impenetrable branchlets, rendered unsightly by the pau- 

 city and smallness of the leaves. One frequent shrub, belonging to 

 the Lahiat(x, had its coarse blackish branches seemingly devoid of 

 leaves ; these on closer inspection being found reduced to mere herba- 

 ceous granules. 



The nearest approach to a tree was a sort of agglomerated shrub ; 

 having in one instance a trunk a foot in diameter, that after rising 

 only two inches, separated into some thirty stems, the total elevation 

 being that of the surrounding shrubs. 



In the course of an excursion over the "campos" or upland plain, I 

 experienced the difficulty mentioned by travellers, of forming a correct 

 estimate of the size and distance of objects ; there being no means at 

 hand of forming comparisons. A seeming tree in the distance, proved 

 on reaching it to be only a signal-bush ; changed in outline by the 

 lower branches being trimmed oif, but of the same height with the 

 other bushes of the plain ; which in general did not reach above the 

 shoulders of a man walking among them. 



The soil on the " campos" was observed to be a mixture of clay and 

 small pebbles, firmly impacted, destitute of decayed vegetable mould, 

 and in great part bare. This, with the hoariness of much of the scat- 

 tered herbage, and the scanty foliage on the shrubs, may account for the 

 absence of refreshing green in the landscape ; the color of the country, 

 clothed with plants in flourishing condition, being distinctly brown, 

 according very nearly with that of our withered New England pas- 

 tures in November. 



In the extensive tract of sand-hillocks above-mentioned, the soil 



