150 MERRILL, 
as Saccharum, Rotthoellia, Themeda, etc. The primitive agricul- 
turist selects another forested area, usually contiguous to the 
one just abandoned or about to be abandoned, fells the trees, 
burns the debris, and plants his crop. If the abandoned clearing 
becomes reforested, then it is only a question of time when the 
land will again be cleared for cultivation by the "caingin" system. 
If, however, as is most often the case, it becomes covered with 
coarse grasses, the chances are that the area will not become 
reforested. Annually recurring grass fires are purposely started 
either for improving grazing conditions, or to make the country 
more easily traversed. These prevent the reproduction of forest 
conditions by killing the young trees, seedlings, etc., which may 
have become established among the grasses, and, in fact, all 
the plants except those which, like the coarse grasses, are pro- 
vided with deep-seated perennial rhizomes. As the grass-covered 
areas become more extended, the fires often gradually push 
back the edges of the forest by the destruction of the young 
and the mature trees along the edges of the clearing, even when 
not aided by man. As a result in many hilly areas in the Phil- 
ippines one finds the continuous slopes covered with grasses, 
the forest persisting only in the ravines, where, perhaps, the 
original clearings made by man were of comparatively limited 
extent. 
Forest fires, as such, are practically unknown in the Philip- 
pines, except perhaps in some very limited areas. The average 
high humidity, the very rapid decay of fallen leaves, branches, 
trees, etc., and the nature of the undergrowth militate against 
them. ^ To permit the ravages of forest fires in the Philippines, 
climatic conditions in ages past must have been very different 
from what they are to-day, and any great difference in this 
respect, especially in decreased humidity, is exceedingly unlikely. 
Forest fires as a factor in the establishment of the open grass- 
covered areas can hence be ignored. 
In grass-covered areas, protected against fire, it is however, 
only a question of time when forest conditions will again prevail, 
the original vegetation of the country claiming its ovnx. It is, 
therefore, due to the presence of man that the open grass country 
exists here, and to his continued presence that this type of vege- 
tation persists and still continues to extend itself at the expense 
of the forested area. Man "is directly responsible for nearly 
all of the annually recurring grass fires in all parts of the 
Archipelago, very few being started from natural causes. 
