AMAZONIAN VEGETATION 361 



apparently repeated on all of them. For example, 

 many of the trees of the inundated margins of the 

 Tapajoz (some of them undescribed when I first 

 gathered them) I found afterwards on the Rio 

 Negro up to its very sources although none of 

 them inhabit the shores of the Amazon, either 

 between the mouths of those two affluents or else- 

 where. A few recur on the Teffe and other black- 

 water streams entering still farther to the west, 

 and even on similar affluents of the Orinoco. 



Here, at least, would seem to be a case of the 

 vegetation depending on the distribution of the 

 running waters ; but in reality both the kind of 

 water and the vegetation nourished by it depend 

 entirely on the nature of the soil, those rivers which 

 run chiefly through soft alluvial bottoms being 

 turbid, while those that have a hard rocky bed run 

 clear ; and the two classes of rivers are repeated over 

 and over throughout the length and breadth of the 

 Amazon region. Into the black Rio Negro runs 

 that whitest of rivers, the Rio Branco, and imparts 

 to the vegetation of the former, for a little way 

 below their confluence, quite an Amazonian char- 

 acter. 1 The two largest tributaries of the Casi- 

 quiari, namely, the Pacimoni and the Siapa, run 

 nearly parallel through a longish course, and at 

 rarely more than 15 miles apart ; yet the former has 

 clear dark water and the latter is excessively muddy. 

 Moreover, when I explored the Pacimoni to its 

 very sources, I found it divide at last into two 

 nearly equal rivulets, whereof the one had white 

 and the other black water. The true riparial v 



1 Here, for instance, is the only locality throughout the Ki<> NI-LTO fur 

 Romlmx Mmignba, a fine Silk-Cotton tree abounding on the Aina/on. 



