510 The Philippine Journal of Science 1914 
species, particularly Wedelia biflora DC., Cosmos caudatus HBK., 
Vernonia cinerea Less., and Eclipta alba Hassk. In the shallow 
water in front of it there may be a little Sesbania, which can 
withstand a greater degree of submergence than Panicum repens 
L., while the latter can develop on drier ground to better 
advantage. 
In the wet open flat area in the center of the Tarlac region, 
there is a large tract of ground covered with Panicum repens L., 
mixed with Paspalum longiflorum Roxb., Panicum amplexicaule 
Rudge, Panicum ( Echinochloa ) crus galli L., Panicum ( Echino - 
chloa) stagninum Retz., and probably other grasses, whose iden- 
tity was not evident from the lack of flowers. Grass for forage 
is obtained from this area, and parts of it are used for pasture. 
These conditions maintain Panicum repens, which otherwise 
would be replaced by one of the Phragmites, Sesbania, or Acros- 
tichum associations, all of which are present in the immediate 
vicinity. 
In the Los Banos area, the maintenance of a rifle range is 
responsible for the continued existence of this association in 
the wetter parts of the flats near the stone quarry. The Pani- 
cum is rather low, seldom more than 30 cm in height. The 
ground is densely carpeted, but the lax flower stems are openly 
disposed. But few species are associated with Panicum; for 
example, Wedelia biflora DC., Panicum ( Echinochloa ) colonum 
L., and Commelina nudiftora L. 
The Panicum repens association tends to spread into the 
Cynodon, while it may be replaced by a number of associations, 
particularly as the water content of the soil is reduced. Al- 
though the area may be burnt over once each year, most of it 
is very low and consequently too wet for the healthy development 
of cogon grasses. 
THE COGON ASSOCIATION 
The cogon association, a common secondary association of this 
part of the world is very sparingly represented in the hot springs 
area, as the ground is too wet. In small patches of higher 
ground which have been burnt over, cogon, Imperata cylindrica 
koenigii Benth., obtains a foothold and spreads rapidly through 
the burnt area. As the dry stems of Fimbristylis miliacea Vahl 
are more easily burned than others, the cogon association has 
seemed more likely to follow that association. 
The Imperata consocies. — The Imperata consocies is entirely 
typical, consisting of a dense growth of a grass, Imperata cylin- 
