476 A NATURALIST IN THE PACIFIC chap. 



these from the tropical west coast of South America until within 

 four degrees of the equator, and then with startling suddenness 

 the dominion of the mangrove begins, the neighbouring hills com- 

 mence to be clothed with tropical jungle, and the climate is 

 completely changed. Mr. John Ball, who sailed along this coast 

 about twenty years ago, referring to this remarkable phenomenon 

 on the borders of Peru and Ecuador, remarks that no such abrupt 

 and complete change both in climate and vegetation is known 

 elsewhere in the world, and he adds that few parts of the American 

 coast better deserve careful examination {Naturalist in South 

 America). This subject has since been discussed at length by 

 Dr. Wolff in his " Geografia y Geologica del Ecuador," and by 

 Baron von Eggers in a paper to be subsequently quoted, two very 

 competent observers, but the latter considers that the subject still 

 requires a systematic investigation, and suggests that an observing 

 station should be established on this coast by the combined 

 meteorological societies of Europe. A sojourn of more than a 

 week in the swamps at Puerto Bolivar, a few miles from Tumbez, 

 enables me to appreciate the nature of the problem, and to throw 

 a little light on the line of investigation required. 



But to return to the general subject of the littoral floras of the 

 west coast of South America, I may say that beginning with the 

 island of Chiloe in lat. 42 S., this coast may be divided into 

 four zones. 



(1) The Convolvulus soldanella zone of Southern Chile, which 

 extends as far north as Coquimbo about 30° S. lat. 



(2) The Plantless or Desert zone stretching north to the 

 vicinity of Arica in lat. 18° 30', and corresponding to the coast of 

 Northern Chile. 



(3) The Sesuvium zone, extending north from Arica to the 

 4th parallel of south latitude in the vicinity of Tumbez, a sea- 

 border of semi-sterility that comprises the entire coast of Peru. 



(4) The Mangrove zone, stretching from Tumbez, on the 

 frontiers of Ecuador, to the equator and on to Central America, 

 but interrupted at first by a strip of sterility on the coast ex- 

 tending from the Gulf of Guayaquil to the borders of Colombia, 

 or, strictly speaking, to the equator. 



The Convolvulus soldanella Zone (Southern Chile). 



This zone, which answers to the coast of Southern Chile, from 

 Chiloe as far north as Coquimbo, corresponds to watered and 



