Notes on Plants at Roraima. 149 
each of these rivers collects its headwaters from unusual- 
ly widely separated localities, and it often happens that 
two or more of these rivers draw some portion of their 
headwaters from unusually contiguous localities. Thus 
it is conceivable, and even probable that any peculiar 
vegetable forms, or animal forms, which may originate 
at one of these localities which supply water to very 
divergent river systems, may distribute themselves over 
very wide areas by passing along the courses ot the 
various rivers arising there. 
It happens that the rock-pillars of the Roraima group, 
rising some 5000 feet over the general level of the sea, 
pour down from their summit streams which go to swell 
the Orinoco, the Essequibo and the Amazon, in other 
words the three rivers respectively of Venezuela, Guiana 
and Brazil. 
Now, as has been already indicated, the flora of 
Roraima is of a very remarkably peculiar character. A 
most interesting question, still awaiting solution, there- 
fore arises, as to the relation of this flora of Roraima to 
the floras of Venezuela, Guiana and Brazil. 
No answer, I say, has yet been attempted to this 
question ; nor can I pretend to suggest that answer. I am, 
however, able to give, as data to be considered in the ques- 
tion, some very general account ot the flora of Guiana, 
and a rather more special account of the flora of 
Roraima in its relation to that of Guiana. 
Guiana, as has been said, rises gradually from the 
east toward the high table-land of the interior of the 
continent. But now, instead of thus placing ourselves 
in imagination on its seacoast and looking westward 
up its gradual slope, let us imagine ourselves on the 
