148 MERRILL. 
their range after once being introduced. Some of these were 
undoubtedly introduced in dirty grain, but for the most part 
probably by natural causes; by winds, and especially by the 
transmission of their small seeds in mud on the feet or feathers 
of migratory birds. Thus directly and indirectly, through the 
agency of man, many species have been added to the flora of 
the Archipelago. Likewise through the agency of man, espe- 
cially in the destruction of the original vegetation over vast 
areas, it is very probable that many local indigenous species 
have been exterminated. 
When, then, we consider the nature of the geological forma- 
tion in and about Manila, the alluvial plain, the dry hills of 
water-laid tuff covered with a thin poor soil, the lack of alti- 
tude, the uneven distribution of rainfall through the year, 
causing a protracted very dry season, the entire lack of forests, 
and the fact that primeval conditions as to vegetation are not 
to be found in the entire area, a flora of approximately 1,000 
different species, or, excluding the cultivated ones, 780 indige- 
nous or naturalized ones in an area not exceeding 100 square 
kilometers, cannot be considered a poor one so far as individual 
species are concerned. 
In fact, as to the number of species, the flora of Manila com- 
pares very favorably with that of like areas in the Archipelago 
supporting a primeval vegetation. Mount Mariveles, just across 
the bay from Manila, is densely covered with unbroken forests, 
and its vegetation, except for a narrow coastal strip, has not 
been disturbed by man. In contrast to the 1,007 species known 
from Manila and vicinity, or excluding the cultivated forms, 
782 native or naturahzed ones, only about 1,114 are known from 
Mount Mariveles, although the latter has the climatic advan- 
tage of 1,400 meters of altitude, is densely forested, and supports 
several types of vegetation that are quite absent in and about 
Manila. 
Properly to understand the local conditions as to vegetation, 
the fundamental differences between the flora of the settled and 
cultivated areas in contrast to that of the undisturbed regions 
supporting a primeval vegetation, and the enormous influence 
man has had on the present condition of the vegetation of the 
Archipelago, it is necessary to take into consideration the prob- 
able nature of the vegetation before the advent of man. 
Considering the Philippine Archipelago as a whole, at the 
present time approximately thirty-three and one-third per cent 
of the entire land area is covered with virgin forest, sixteen and 
