136 



DISTRIBUTION OF PLANTS. 



was asserted by our guide to be smoke. But leaving on either hand 

 the more distant snowy peaks, the eye rested mainly on the enormous 

 mountain-mass directly opposite; a scene of grandeur and desolation. 



We met some horsemen conducting a dozen mules laden with snow, 

 on their way towards the distant city ; and about two hours before 

 dark, we arrived at the source of supply ; an extensive permanent 

 bank of hardened snow. We hastened to dismount, for a nearer view 

 of the mode in which aridity, combined with Alpine elevation, had 

 been provided for in the vegetable growth. 



Congested patches of UmheUiferm, hardly distinguishable from those 

 of Terra del Fuego, showed at once, that the Alpine habit of growth is 

 independent of the proportion of moisture. These patches proved 

 however more densely impacted and indurated than I had supposed 

 possible in the vegetable kingdom; being as hard and even as a floor; 

 and specimens had to be procured with a hammer, by breaking frag- 

 ments from the margin. 



Here and there in the Desert, cakes of less congested herbage 

 seemed at a distance more luxuriant. On approaching, the botanist 

 found only an increase of difficulties ; the component plants being 

 spinescent, presenting on all sides thorns, not of the ordinary pointed 

 kind, but intensely sharpened, so that the least touch drew blood. If 

 plants of a different character were sometimes present, these grew 

 intermingled and unapproachable in the midst of armed protection ; 

 and notwithstanding every precaution, each specimen here collected 

 literally took its revenge in blood. The spinescent beds, two to three 

 inches high, were each made up of a single kind of plant : the most 

 frequent being the Chuquiraga^ more congested than below, and alto- 

 gether depressed to the prevailing level ; two species of Nassauvia, 

 excessively troublesome from the acuteness of the points of their 

 leaves; a second species of the gen. Legum. with branching spinescent 

 phyllodia ; and an Adesmia, presenting above and around nothing but 

 a cake-like chevaux-de-frise of branching thorns. 



One of the yellow-flowered Senecios, devoid of any spinescent ten- 

 dency, yet conformed in outline ; and grew in widely-detached, con- 

 gested, cake-like beds. The Epliedra, too, frequent at intervals all 

 the way from the sea-coast, had at last assumed the same congested 

 mode of growth, in detached Alpine cakes. 



Another form of adaptation was remarked ; in a tendency to pro- 

 duce long, close-set hairs, like a furry envelope. Here and there in 



