OlS" THE BOTANY OF WESTERN SOUTH AMERICA. 137 



Notes on the Botany o£ Western South America. 



By John Bxti, F.E.S., F.L.S. 



[Read 18th February, 188G.] 



In the course of a hurried journey round South America, I 

 visited, in 1882, some points, chiefly on the western coasts of that 

 continent, of which the vegetation is imperfectly known ; and I 

 have since endeavoured, by comparison of the available materials, 

 especially those preserved in the herbarium at TCew, to clear up 

 some doubtful questions relating to the distribution of species- 

 I have thought it desirable to bring together such of the notes as 

 I have made on particular places visited by me as appeared to 

 contribute some slight additions to our existing knowledge, or to 

 correct errors that have crept into works of authority. 



Before entering into details, however, I Avould premise a few 

 remarks on the climatal relations of the western sea-board of 

 South America, which have had such a remarkable influence on the 

 development of organic, and especially of vegetable life. For an 

 accurate knowledge of the chief factors of climate — temperature 

 and rainfall — we are unfortunately at a great disadvantage; for 

 there are few equally extensive regions of the earth where meteo- 

 rological observations are so scanty and so imperfect as on the 

 west coast of tropical South America. So far as I know, none 

 whatever are available from any point on the coast between 

 Panama and Lima, a distance of fully 1600 miles ; and our know- 

 ledge of ihe climate is derived merely from the testimony of 

 travellers and the few Europeans who have resided in the country. 



The Isthmus of Panama (between 9° and 10° N. lat.) has an 

 annual mean temperature of about 81° F., rarely varying more 

 than two or three degrees above or below that average. The 

 rainy season extends for seven months, from May to November, 

 with an average monthly fall of about 8^ inches, while during the 

 relativel}^ dry season, from December to April, the total rainfall 

 for five months reaches the same amount, giving the rainfall in 

 the year about G8 inches. The climate of the coast of 

 said to retain the same general characteristics ; but as we travel 

 southward towards the equator the length of the rainy season 

 gradually increases, until, in the G-ulf of Choco and the adjoining 

 const, there is no season of even relative dryness, and heavy rama 

 occur frequently throughout the year. The reports to this effect 



Darien 



