O77 
other places near the sea level. This difference is in direct response to 
the less-pronounced dry season in these situations. Thus, on the east 
coast of Tayabas (sub-province Infanta) trees such as Dipterocarpus 
grandiflorus of the Dipterocarpus-Shorea formation, Agathis philippi- 
nensis of the Shorea-Plectronia and Tristira decorticata of the Eugenia- 
Vaccinium are fairly represented in the forests below 100 meters. On 
the east coast of Mindoro, Shorea polysperma and Shorea contorta are 
not only present near sea level but in many places they have succeeded 
in obtaining a foothold on old beach lines. In this portion of the Island, 
also, Asplenium nidus, Ophioglossum pendulum and associated species 
are present at the same lower altitude and in the valley of the Tinguan 
River, in the sub-province of Infanta, near sea level, Myrmecodia echinata, 
Nepenthes alata, other related epiphytes and Decaspermum panicu- 
latum, are encountered. ‘These examples suffice to illustrate the fact that 
many plants found on the upper slopes of the mountain are also present 
near the level of the sea when the moisture conditions are favorable for 
their existence in this situation. Again, so far as my observation goes, 
in those places in which the dry season is less pronounced, the very 
characteristic bamboo forests at the base of Mount Mariveles are entirely 
absent, being replaced by forests which show a very much less deciduous 
element. Thus, portions of the east coast of Luzon have no bamboo 
forests, whereas they are present in other parts where the dry season is 
pronounced. Parkia rorburghii, while it is found scattered in evergreen 
forests on the east coast of Mindoro, nevertheless shows a change in habit. 
Instead of being deciduous for two or three months, as is the case at 
Lamao, there, in many instances, the new leaves appear as soon as the 
old ones have been shed, and on the dry, sandy soils of old beaches, the 
interval of time between the shedding of old and the appearance of new 
leaves was at the time of observation, never more than two weeks. 
Relations to topography.—In the discussion of each climatic forma- 
tion, attention has been called to the physiographic situations in which 
the vegetation is less or more mesophytic. Thus, exposed ridges and 
steep exposed slopes have not only drier soils but drier atmospheres, 
and consequently the vegetation in these places is much thinner and 
more xerophytic. As the physiographic forces at work bring them into 
more stable and less exposed conditions, their vegetation will lose its 
xerophytic character and gradually assume that of the climax vegeta- 
tion of the formation. The main rivers draining the mountain, cut 
the climatic formations at right angles and in their beds and in the 
cafons thus formed, a local climate which is more or less nearly uniform 
throughout the length of the stream, is produced. The ecological char- 
acter of the vegetation throughout such river beds and those of the side 
streams is alike and the latter shows closer relations than are to be found 
in any one formation in relation to the other vegetation in that formation. 
This is due to both edaphic and atmospheric characters. The proximity 
