162 A NATURALIST IN THE GUIANAS 



of smooth or rounded surface no vegetation exists, but 

 wherever there are hollows in which a bit of mould has 

 collected there is sure to be some sort of growth, and in 

 proportion to the depth of this layer of vegetable matter 

 is the luxuriance of the growth which covers it. The 

 flora of these open masses of plutonic rock is so different 

 to that of the surrounding country, that the traveller 

 might well believe himself to be in another region 

 thousands of miles away from the gloom of the forest 

 with its huge trees, through which he had passed but a 

 few minutes before. Several kinds of orchids are met 

 with in such places. Some grow on the rocks alone, 

 while others occur only on the moss-covered branches of 

 the stunted trees, all knotted and gnarled peculiar to this 

 vegetation, Cattleya superba and Epidendrum Stam- 

 fordianum, both of which are abundant in these places, 

 attach themselves to trees and rocks. In the case of the 

 former orchid, however, only a small number of plants 

 are seen on the rocks, by far the greater proportion 

 being found on the branches or trunks of trees. It is the 

 opposite with Epidendrum Stamfordianu^n, which grows 

 in such luxuriant profusion all over the rocks in certain 

 parts of the lajas, that thousands of plants might be 

 collected in the course of a single day. A very fine 

 Oncidium and a large Catasetum also form part of this 

 flora, but while the Catasetum is fairly abundant the 

 Oncidium is rather rare. Epidendrum elongatum is 

 another orchid which grows in large masses on the 

 lajas, some of the masses being several square yards in 

 extent. As this Epidendrum is very free in blooming, 

 and its flowers vary in shade from light pink to the 

 darkest scarlet, the effect produced by the brightness of 

 colour against the sombre background of black granite is 



