679 
sandy beaches, which have an especial vegetation more or less inde- 
pendent of the climate in which it grows. Cowles ®* enlarges this idea so 
as to include all types of topography in the process of destruction and 
which, consequently, in their present condition, offer unstable and there- 
fore temporary habitats for plants. The vegetative condition will 
become stable only when base-level conditions are approximated. Thus, 
the canons on the one hand have a temporary, mesophytic vegetation 
and the steep slopes a temporary xerophytic one. The top of the moun- 
tain is exceedingly unstable and therefore the vegetation is temporary. 
Traced to its logical conclusions, the physiography of the entire 
mountain is very unstable and therefore the vegetation is temporary. 
With its destruction, it will pass to a more and more permanent condi- 
tion and the vegetative types will be altered with the change in topog- 
raphy; the climate will then also be different and will more nearly 
approximate that at present prevalent at the base; and therefore the 
erosive topography at old age will have a vegetative condition not unlike 
that of the Bambusa-Parkia formation. Just before the death of such 
a topography, the whole country will be brought nearly to a base-level 
with the ground water not far from the surface. The vegetative condi- 
tion will then be not unlike that of a delta region, of which there are 
many fine examples in the Philippines. At death itself, the mangrove 
swamps will probably prevail. Of course, the above are only theoretical 
considerations, yet these erosive stages are approximated in different 
parts of the Islands so that when logically united the genetic relations 
of the different vegetative formations can be mage clear. 
(The work on which this paper was based was performed while the 
writer was a member of the staff of the Bureau of Science. It was in 
part written after his transfer to the Bureau of Forestry.) 
* Cowles, H. C.: The Physiographie Ecology of Chicago and Vicinity. Bot. 
Gaz. (1901), 31: 75. 
