10 BULLETIN 134, UNITED STATES NATIONAL MUSEUM 



" During the wet season, beginning usually about the latter part 

 of May and ending about the first of December, southerly winds 

 become dominant and rains are more general throughout the Isth- 

 mus. At the Canal Zone, which is a cross-section of the Isthmus 

 about 50 miles in extent, the annual rainfall on the Atlanic coast 

 is about double that on the Pacific coast. Official records for 1909 

 show a total rainfall of 93.06 inches at Balboa, and 183.41 inches at 

 Cristobal; but the average for 13 years at the former station is 71.67, 

 and for 40 years at the latter station 130.03. This relative humidity 

 of the two sides probably obtains as far west as the Costa Bican 

 frontier, but in eastern Panama the difference is less marked. In 

 much of the Darien region the total rainfall is increased to an an- 

 nual precipitation of perhaps more than 200 inches which renders 

 this area one of the wettest in America. 



'• Under the stimulating influence of frequently recurring showers 

 and continuously moist conditions throughout the year, the At- 

 lantic watershed maintains a much more exuberant growth of vege- 

 tation than the Pacific watershed, where long periods of drought 

 check vegetative vigor. At the height of the dry season these cli- 

 matic differences are manifested in the contrasting aspect of the 

 forests on the two slopes. While the trees of the Atlantic forest 

 are clothed with brilliant evergreen foliage, those of the Pacific 

 forest, truly deciduous for the most part, present bare stems and 

 the landscape has an autumnal appearance, relieved to some extent 

 along the borders of the streams. It is in this dry forest that one 

 notes the strange habit, possessed by various unrelated species, of 

 producing flowers and ripening fruits while the trees are in a leaf- 

 less condition." 2 



Plant and animal life. — Zoologically, southeastern Panama be- 

 longs to South America rather than to North America. The north- 

 ward course of the great rivers of Colombia and the adjoining north 

 coast of South America with its island outposts facilitates the trans- 

 fer northward of plant life as well. 



The southern and eastern provinces of Panama have a fauna 

 typically South American, while the fauna of the north and west 

 is Central American, the two types meeting at the narrowest and 

 least elevated part of the Canal Zone. Although there are no dis- 

 tinct lines between these faunal zones, certain species are never 

 found west of the canal and others never occur to the east of it. 



Some of the animals frequenting the Pacific side of Panama are 

 species of deer, jabali or peccary, paca, tapir, curassow, and various 

 game birds. Along Tuyra River on the Pacific coast every iso- 

 lated tree has great numbers of long, pendant, pouch-like nests of 



2 Smithsonian Miscellaneous Collections, vol. GO, No. 5, p. 23. 



