298 
The Philippine Journal of Science 
for the sake of their own proper development even before they 
begin to perform any considerable photosynthetic work. Dur- 
ing the day, they occupy a position where they get whatever 
advantages the light may bring; while the oldest parts perma- 
nently assume this position. At night, when the exposure to 
the light and its advantages is impossible, they assume a position 
in which they are protected from the dangers incidental to the 
day position. 
