THE PHILIPPINE 
Journal of Science 
C. Botany 
Vol. IX NOVEMBER, 1914 No. 6 
SWAMP VEGETATION IN HOT SPRINGS AREAS AT LOS BAnOS, 
LAGUNA, P. I. 
By Frank C. Gates 
(From the College of Agriculture, University of the Philippines, 
Los Banos, P. I.) 
Five plates 
Just west of Los Banos, Laguna, P. I., extending from near 
Mount Maquiling, an extinct volcano, north to Lake Bay is a 
low swampy region, about 100 hectares in extent, in which 
thermal areas are present near the foot of the mountain. From 
the majority of the pools of hot water small streams run to 
the lake for most of the year. During the latter part of the 
dry season the water-table level may be so lowered that no 
streams run from many of the pools, while some of the pools 
may even dry up. 
The temperature of the hot water is always distinctly above 
that of the air. In the middle of the hot season of 1913, pools 
from which no streams were running had a temperature of 
from 37° to 41.5° C., while at the points of emission in others 
the thermometer registered between 70° and 80°. With the 
advance of the rainy season, the temperature of all the pools 
increases to a greater or less extent, the minimum being about 
46° and the maximum 91.2°. Most of the pools vary between 
81° and 87°. After the rainy season is well established, tem- 
peratures seldom exceed 87°. 
The swamp region is now conveniently divided by the railroad. 
The eastern part of the area will be designated the Los Banos 
hot springs, and the western part — much the larger — the Tarlac 
area, from the adjacent barrio, Tarlac (or Tadlac), a fishing- 
village on the shore of Lake Bay. At the Los Banos springs 
the rifle range and drainage ditches interfere with the com- 
pletion of the normal plant successions. The Tarlac area is 
