500 The Philippine Journal of Science 1914 
and soon develops into typical clumps. Before it has obtained 
complete dominance Acrostichum aureum L. is likely to invade 
the area from the edges. 
The high hot water of 1914 materially extended the areas of 
the flats in the vicinity of the Los Bajfios springs by killing 
back considerable Acrostichum. As a result of this high hot 
water much of the Bacopa between the clumps of Fimbristylis 
was killed, and the appearance of the area was materially trans- 
formed from one of Bacopa with some Fimbristylis here and 
there to an area with scattered clumps of Fimbristylis, a little 
Bacopa near the edges, and a few dead ferns near the margin. 
As complete, prolonged submergence of a clump of Fimbristylis 
is necessary to cause death, this year’s high hot water hastened 
the elimination of Bacopa, while the destruction of Acrostichum 
was really favorable to the extension of Fimbristylis, causing a 
reversal of the normal genetic’ succession. 
This association, represented by etiolated plants of Lippia only, 
also occurs on the tension line between Typha in the water and 
talahib, Saccharum spontanewm L., on the railway embank- 
ment. Bacopa readily remains as a relic in succeeding associa- 
tions which do not cut off too much light. : 
Occasionally the Acrostichum association seems to invade 
Bacopa directly along the banks of streams, but usually one or 
more associations intervene. The same is true with respect to the 
parang association. The relationships of the Bacopa-Lippia as- 
sociations are best seen at the Los Bajios hot springs where 
there is less fluctuation of the water level. In the Tarlac area 
the high hot water each year kills back the Bacopa clear to the 
shrubs, under which it cannot persist during the dry season. 
During the dry season there is usually some Bacopa around most 
of the hot springs in this area—especially those nearer the 
margin of the swamp. Only a very little Bacopa is enabled 
to persist to restock the area, due to the fact that much of it 
is killed back each rainy season, and that the areas in which 
the plant thrives are covered with water for a period after 
the rainy season, thus preventing natural reproduction of the 
plant. 
This easily explains its scarcity in the Tarlac area. High 
water itself usually does not kill Bacopa unless the temperature 
goes above 52°, for Bacopa will grow upward with the rising 
water. It partly floats on the water and partly rests against 
other plants. In case the water rises very rapidly so as to 
drown most of the plants of Bacopa, there are always detached 
pieces of stems which float to the surface and grow there. 
