ix, c, 6 Gates: Sivamp Vegetation in Hot Springs Areas 511 
drica koenigii, with no regular secondary species. The consocies 
does not have a firm grip on the land and considerable evidence 
of successions from it are visible. Acrostichum spreads into 
it along the margins and even into the very center of the grass 
area, because the wet soil is more favorable to Acrostichum 
than to Imperata. As this latter association is rather open, it 
does not generally annihilate the cogon, but becomes the domi- 
nant species with the cogon persisting as a relic. • Either directly 
or through an Acrostichum stage the cogon passes into the 
parang association. Acacia farnesiana Willd. obtains a foot- 
hold and develops readily. As soon as it becomes higher than 
the cogon it exhibits its ability to shade the cogon out of exist- 
ence. This may be entirely accomplished within a year under 
favorable circumstances. If fires did not occur during the dry 
season the cogon would very shortly become nonexistant, as 
conditions are so much better suited for other plants. 
The Saccharum consocies . — The Saccharum consocies, domi- 
nated by talahib, Saccharum spontaneum L., hardly occurs in 
the hot springs area proper, but is abundant on the ballast 
of the railroad through the area. It shows no successional re- 
lationship with the hot-springs vegetation, being separated from 
it by sharp tension lines at the limits of the railway ballast. 
THE PARANG ASSOCIATION 
The normal association to succeed a number of the associa- 
tions treated of above, consists of shrubs and small trees. For 
the most part, in the Tarlac area, this association is on the 
border of the swamp rather than in it; while at the Los Banos 
springs, on account of the permanent lowering of the water 
by ditches, this association is actively invading the swamp area 
and radically changing its structure. In the Tarlac area, al- 
though the tendencies are clearly indicated, succession is very 
slow and barely taking place, on account of the pronounced 
fluctuations of the water level. The wetter areas are most easily 
invaded by the Acacia and the Premna consocies. 
The Acacia farnesiana consocies . — Invading the water-soaked, 
Acrostichum - dominated ground in the vicinity of the quarry 
in the Los Banos area, are a number of shrubs of Acacia farne- 
siana Willd. which have sprung up in the spaces between the 
plants of Acrostichum and, growing higher than them, are 
shading them out of existence. The canopy developed by Acacia 
has permitted relatively few plants to become very important 
in effecting succession. In point of relative abundance, about 
130416 — 2 
