xxxii THE COAST OF ECUADOR 485 



kilometres from the sea it passes gradually into a region of 

 extensive bare mud-flats which are penetrated by salt-water creeks, 

 two or three yards across and a foot or two in depth, that are 

 bordered by low and shrubby Avicennias, the Salicornia bushes 

 above noted, and dwarfed trees of Rhizophora mangle only four or 

 five feet high. These flats, which are evidently only overflowed by the 

 sea at the higher spring tides, were at the time of my visits much 

 sun-cracked and in some parts incrusted with salt ; but the mud 

 was rather soft, and in places Sesuvium portulacastrum and 

 Batis maritima flourished in quantity on it. These mud-flats, about 

 two kilometres across, pass by degrees into the low-lying level 

 district known as the Machala plains, on which the capital of the 

 province is built. Here the soil is dryish, and, notwithstanding 

 that it displays on its surface when exposed to the sun a white 

 saline efflorescence, a dry jungle type of vegetation of the 

 xerophilous character here thrives. I noticed casually the 

 Algaroba (Prosopis), a yellow-flowered Cordia, cacti of the 

 Opuntia and Cereus kinds, besides several small trees and shrubs 

 often thorny. 



These Machala plains, on account of the fine saline incrustation 

 above mentioned, are of much interest, since at a distance of six 

 kilometres from the coast they thus display on their surface the 

 effect of sea-water infiltration, their level above the sea being 

 only a few feet. We have seen the three stages of this infiltration 

 landward of sea-water : first, the mangrove-swamps daily over- 

 flowed by the tide ; second, the mud-flats behind them which are 

 only overflowed by the fortnightly spring-tides ; third, the 

 vegetated plains behind all, which are sufficiently raised to be 

 above the reach of the tides, but which are nevertheless soaked 

 with sea-water that displays its presence in the salt left by 

 evaporation on the surface of the soil. 



But another interesting point is here raised. At the back of 

 the mangrove-belt, in most parts of the world, we usually find a 

 particularly rank and luxuriant vegetation where the Scitamineae 

 often take a leading part ; whereas on the sea-border of this part 

 of Ecuador the mangrove-swamps pass gradually into arid 

 saliniferous plains. With this singular fact is to be associated the 

 circumstance that we see here in operation, some four or five miles 

 from the coast, a process by which great quantities of sea-salts are 

 accumulating below the surface. This may possibly be concerned 

 with the origin of the great saline deposits of Northern Chile. 

 However this may be, there is some reason for believing and I 



