TRANSACTIONS OF SECTION E. 319 



in one latitude and the western in another. Contrast with 

 this luxuriant arboreous vegetation — resulting, as I contend, 

 from heavy rainfall — the barrenness of Peru and northern 

 Chili, the treeless condition of the pampas of La Plata, Banda 

 Oriental, and Patagonia, and the deserts of Utah and Nevada, 

 in all of which countries the mean annual rainfall is less than 

 lOin. (Gin. at Fort Bridger, Utah; 5in. at Fort Cliurchill, 

 Nevada ; 4in. at Mendoza, La Plata ; and Oin. at Luna). 



Darwin, in his "Journal of Researches " (p. 46), a iiropos 

 of the entire absence of trees in Banda Oriental, notices inany 

 of the above facts respecting South America, and discusses the 

 question with which we are engaged at some length. He thinks, 

 as I have already remarked, that extremely level countries 

 such as the pampas seldom appear favourable to the growth of 

 trees, and that this may be possibly attributed to the force of 

 wind or kind of drainage. The fact is, however, that quite 

 recently the Eucalyptus globulus has been extensively planted 

 in different parts of the pampas, and, being a tree that can 

 stand drought well, it succeeds despite the pampero, even 

 better than in Australia, becoming both richer and denser in 

 foliage. But, apart from this experimental proof that Darwin 

 was in error on this point, it must be observed that the most 

 extensive tracts of level country w^ith which we are acquainted 

 are flanked on their western sides by mountain-chains cutting 

 off the oceanic winds and rains (Guyot's " Eartli and Man") ; 

 and this factor, from the point of view of one who believes that 

 rainfall determines forest, is not to be lost sight of. I confess 

 I do not see that the argument as to force of wind and 

 drainage in level tracts is very cogent. Darwin himself subse- 

 quently records that he found little or no vegetation whatever 

 on the Sierra de la Ventana — a group or chain of hills 3,000ft. 

 high on the eastern side of the Patagonian plain and at no 

 great distance from the South Atlantic. Now, the treeless 

 uniformity of Patagonia ought to have been broken by this 

 elevated ground, if Darwin's reasoning was conclusive ; for 

 shelter would be found either on one side or another of the 

 chain, and drainage would be generally good on its slopes. 

 Darwin refers to Maclaren's article in the "Encyclopaedia Bri- 

 tannica " as " inferring with much probabilit}'' that the presence 

 of woodland is determined by the annual amount of moisture," 

 and emphatically says that, confining our view to South 

 America, we should certainly be tempted to believe that 

 trees flourished only under a very humid climate, for the 

 limit of the forest-land follows in a most remarkable man- 

 ner that of the damp winds. He seems, however, to attach 

 importance to the fact that the Falkland Isles can boast 

 of few plants deserving even the title of bushes. Such 

 carefulness about making wide generalisations is eminently 



