8 BOTANICAL GAZETTE [JANUARY 
the forest reigns, the soil is richer in water, and it is my 
opinion that the water after all is the most essential cause of the 
distribution of plants, the physiognomy of the vegetation, and 
the ecological stamp of the vegetation formations. It has been 
very much disputed whether it is the chemical or the physical 
qualities of the soil that are the principal causes for the distribu- 
tion of plants; as to the vegetation formations it is my 
opinion that we find the principal cause in the quantity of water 
the soil is able to receive and keep, no matter whether this is 
owing to physical or chemical causes. Difference in richness in 
water was the condition for the occurrence of these two forma- 
tions, but in the course of time the forests improved the soil by 
their own work, constantly accumulating more or less of humus. 
In the campos, on the contrary, the sun desiccates the fallen 
leaves, which crumble into dust and disappear. One thing more; 
the forest gives shade to a good many species that are not able 
to endure intense light. Hence the forest affords physical con- 
ditions for a vegetation that is not to be found in the campos, 
and most likely this is the essential cause of the great richness 
of the forests in species. Favorable conditions of vegetation 
seem also to entitle one to suppose a more profuse origination of 
species. 
If we compare the Brazilian campos with similar regions in 
another part of South America, the Venezuela savannas, which 
seem to possess the very same physical conditions and where a 
corresponding vegetation has developed itself, I believe we 
shall learn to some degree the importance of /zstorical facts. A 
few months ago I traveled in Venezuela. At the sight of the 
savannas I was overcome with the greatest surprise and even joy. 
Never should I have expected to find such a striking conformity 
with the Brazil campos. I felt as if. I were removed to the 
campos near Lagoa Santa, thirty degrees of latitude south of 
Venezuela, and there arose in my memory the happiest years of 
my youth, 
When one is traveling from Puerto Cabello through the 
country to Valenzia, and has reached the high passes of the 
