154 SOUTH AMERICA 



lakes, the reed vegetation is constantly encroaching, 

 building floating islands of intertwined reeds, natural 

 rafts called sudd, which sometimes support trees and are 

 torn and carried away in times of flood. Such sudds, 

 floating down lakes and rivers, are a common sight. 

 Some of the rivers, even the Pilcomayo, lose themselves 

 in impassable swamps, where the firm ground and the 

 loose muddy floating islands are hard to distinguish. 

 When the ground dries up, the reeds shrivel and dis- 

 appear. A short grass, followed at first by a carpet 

 of low, and later on by a crop of tall, herbs and bushes, 

 springs up, affording succulent grazing grounds for horses 

 and cattle, but sadly infested by myriads of mosquitoes 

 and other pests. 



The river banks disappear under hedges of tall canes, 

 wavy reeds, and bambus, so that dikes and sand-banks 

 thrown up by the waters are, in many cases, the only 

 dry roads. These are soon clothed with a luxuriant 

 covering of herbs, thanks to the seeds carried by the 

 streams and scattered in the mud and sand. Bushes 

 and trees strike and grow quickly and deck the levees 

 with impassable low jungles, recalling our osier beds. 

 The islands thus enclosed by the dikes become wet 

 meadows or grass moors strewn with ' banados '. They 

 may be locally dotted with thin copses of bushy acacias, 

 or give rise to palm forests. 



Such is the power of those changeful and unsettled 

 rivers that the surface of the country is in constant 

 process of transformation by the periodical flooding of 

 the pampas or the draining of marshes, but the banks 

 along the streams may be firmly held together by the 

 vegetation and even become permanently wooded. Ad- 

 vantage is taken of this by man for his settlements 

 roads, and railways: thus it happens that frequently 



