xxxii THE COAST OF PERU ' 481 



Under such conditions my investigation into the seed-drift 

 was out of the question ; but I saw what would be considered by 

 some as more interesting, namely, the dead of many latitudes piled 

 up on the beach by the Humboldt Current. 



The Sesuvium Zone (The Peruvian Coast). 



This zone, which comprises the whole Peruvian sea-border from 

 Arica in i8°3o' S. to the vicinity of Tumbez in about 3°3o' S., 

 usually possesses in its scanty littoral flora one or two species of 

 Sesuvium, and in some places Sesuvium alone occurs on the 

 beach. The beaches here do not line a region of almost complete 

 aridity, as in the coast corresponding to the great desert region of 

 North Chile. Though here also scarcely any rain falls, the sea- 

 border receives the benefit of the " garuas " or drizzling sea-fogs ; 

 whilst the region immediately behind the coast may either be desert 

 or semi-sterile during much of the year, or may be scantily vege- 

 tated, or, as along the river-valleys, may display a vegetation more 

 fitting to the latitude. The general aspect, however, of the coast of 

 Peru is one of aridity ; but there are probably few beaches where a 

 certain amount of subsoil drainage from the land sea-ward does not 

 exist. This is well exhibited at Ancon, north of Callao, where in 

 the most unlikely situations water is reached by digging wells ; but 

 in spite of this the Sesuvium alone grows on the beach. The 

 beaches examined by me in the heat of the day in February, as at 

 Mollendo and Ancon, had much the same surface-temperature 

 noticed in the preceding month on the beaches of North Chile, 

 namely, 120' to 130"^ F., and in one place 135° ; whilst at a depth 

 of four inches the sand was rather cooler, and instead of being 

 between 95° and 100°, as on the Antofagasta and Iquique beaches, 

 it was here usually only about 90'. But it was only occasionally 

 that the sand felt at all moist at a depth of five or six inches ; and 

 in this zone, therefore, only a few shore plants of a peculiar type 

 could be expected to find a station on the beaches, excepting, of 

 course, those localities where low marshy districts or lagoons lie 

 behind the beach. 



The beach plants of the coast of Peru as observed by me 

 though usually scanty, presented two types according to the 

 character of the district bordering the beach. I make no mention 

 here of those local plants, often belonging to the Composita;, that 

 as at Callao and Arica descend the valleys to the beaches, or to 

 those numerous introduced plants that accompany cultivation, 

 VOL. II II 



