18 Annals of the Carnegie Museum. 



slope is very different, the vegetation being mostly confined to the 

 river valleys, creek beds, and ravines where there is water. The 

 woods and bushy growth thus appear in strips on the grassy moun- 

 tains. It is thus between San Sebastian and Atanquez, at Rosario, in 

 the Chinchicua range, in the marginal ranges, at Marocaso, and also 

 at San Jose in the valley of the Guatapuri. In fact, on the whole 

 south slope of the Sierra Nevada there is only one large forest, that 

 of the Alguacil on the Chinchicua range above Pueblo Viejo. This 

 is a forest of the cinchona zone, and is always fresh and moist, form- 

 ing a welcome exception to the rule in the southern Nevada. 



Two kinds of humid forest may be distinguished, that of the Upper 

 Tropical and of the Subtropical Zone respectively. Temperate Zone 

 forest, such as is represented throughout the Central and Eastern 

 Andes of Colombia, is practically wanting, at least in that portion of 

 the Sierra Nevada explored by the junior author, timber-line descend- 

 ing as a rule to more or less the altitude at which the Temperate Zone 

 forest begins in the Andes. Whether this circumstance is due to 

 climatic conditions, or to some extent also to a difference in the under- 

 lying rock, is not entirely clear. It has an important bearing upon 

 the character and local range of the alticoline forms of bird-life, as will 

 be pointed out later. 



The forest of the Upper Tropical Zone, as already stated, consists 

 largely of tall straight trees set closely together, and with very little 

 tangled undergrowth as a rule. Palms are not abundant, and grow 

 largely along ridges where there is an outcrop of clay. They are 

 more abundant on the east slopes of the Horqueta and San Lorenzo 

 than on the north and west slopes, also over the whole north slope 

 of the Sierra Nevada proper. The undergrowth consists of shrubs of 

 various species, but very few small palms, such as are so abundant 

 in the Subtropical Zone. Ferns are abundant, but epiphytes are not 

 so much in evidence, neither is there a great abundance of moss and 

 lichens, such as are prevalent in the Subtropical. It is a forest of 

 this character which extends upward to 4,500 feet (more or less), or 

 to the edge of the " Cloud Zone," but does not drop down into the 

 littoral, except for an interval along the north coast, where it actually 

 reaches the sea. 



Naturally there can be no hard and fast line drawn between the 

 Upper Tropical and Subtropical forests, since the one merges imper- 



