PHILIPPINE SOILS. 301 



Not only is a rainfall well distributed throiighout the year a condition 

 absolutely essential to the* success of certain crops such as hemp, coconuts, 

 tobacco, and rubber, but this distribution also controls the prevalence of 

 certain species of plants of the native vegetation. On the other hand, 

 certain species of plants are adapted to a long dry season. The first 

 striking difference in the vegetation of a region often can be referred to 

 climatic variations. In the absence of more exact data, observation of 

 the presence or absence of certain dominant species of plants in a given 

 area may indicate what tlie local conditions are with regard to rainfall, 

 whether abimdant or scanty, but more particularly whether it is well 

 distributed throughout the year or whether there is a long and well 

 defined dry season and indirectly indicates the crop possibilities. A few 

 illustrations will make this clear. 



Mr. Merrill of the Bureau of Science, informs me that there are in 

 the Philippines, as in most other countries, a number of very distinct 

 vegetative types depending on rainfall, altitude, etc., and at low altitudes 

 different types of vegetation are encoiintered which apparently owe their 

 development largely to the equitable or interrupted distribution of rain- 

 fall throughout the year. In the regions contiguous to Manila, in Ba- 

 tangas, and in Mindoro it will be noticed that certain plants are to a 

 greater or less degree dominant, good examples of which are Bauhinia 

 malabarica Eoxb., locally known as alihangbang or calibangbang, and 

 Albizzia procem Eoxb., locally knoAvn as alalangad or acleng parang, 

 these and other species found in similar habitats being apparently well 

 adapted to a prolonged dry season. Although the above species and 

 others characteristic of the dry regions are of wide Philippine and extra- 

 Philippine distribution, they are not found in this Archipelago, or at 

 least only to a very limited extent, in those regions where the rainfall 

 is more equitably distributed: they are either not adapted to regions 

 subject to continuous rainfall, or other more vigorous species crowd them 

 out in the more favored localities. 



In the absence of more authentic data, it seems to be safe to assume 

 that where certain species of plants are dominant, such as those mentioned 

 above, it is an indication that there is a prolonged dry season, and hence 

 that such regions are not adapted to crops requiring a more equitably 

 distributed rainfall, such as rubber, coconuts, hemp, and tobacco. 



Undoubtedly, tliere is also a greater or less relationship between the 

 prevalent species of any given area and the geologic formation, but 

 unfortunately we have not at this date any correlated infonnation, as to 

 the prevalent species in different regions in relationship to the nature 

 of the soil or tlie underlying rock. 



CHEMICAL AN'D PHYSICAL ANALYSES OF PHILl'PPIXE SOILS. 



However important the lines of investigation as to conditions favoi-able 

 to the growth of agricultural plants and however essential the share that 



