93 



cent, falls from May through September. In the rainy season 

 the excess of rain over the needs of the vegetation is considerable. 

 During the northeast monsoon, which blows the rest of the year, 

 precipitation is very deficient and the vegetation withers. The 

 following table summarizes the temperature conditions by 

 months: 





Highest 



Lowest 1 Year 





°C. 



37-8 April 



33.1 April 

 28.0 May 



23.2 June 

 21.7 August 



°C. °C. 



32. ^5 August 37.8 





29.9 August 31.5 

 24.9 January 26.5 

 19.0 January 21.5 

 13.9 January 13.9 



Mean 



Average minimum 



Absolute minimum 



The structure of the association is very simple, as Casuarina 

 is normally the only tree present on the flats. Although the 

 needle-like branches are very slender, in a normal grove the 

 aggregate shade cast is very great. Very few herbaceous plants 

 — largely low grasses, as Eragrostis spartanoides, Eleiisine indica, 



Fig. 3. An opening in a grove of Casuarina, vegetated with the grasses, 

 Saccharum spontaneum and Miscanlhus sinensis. Villar, Zambales Province, 

 December 24, 19 14. 



Panicum patens, and Oplismenus compositus , and "weeds," as 

 Ageratum conyzoides, Amarantlms spinosus, Aneilema vitiense, 

 Anisomeles indica, Cy penis difformis, Desmodium laxifloriim, 



