GIANT BAMBOOS. 
251 
little to do with the changes of growth/" On the other hand 
observations taken hourly in conjunction with readings of the 
psychrometer gave evidence of a marked parallelism between 
the two curves, whilst the curve of temperature had an almost 
exactly opposite character. 
In this connection it is to be noted that in the early part of 
the period of growth when these observations were made, 
drops of water were excreted from the tips of the sheathing 
leaves in considerable quantities during the whole night, 
the night being regularly the period of most rapid growth. 
This rapid excretion of water has been noticed by Molisch.t 
This observer found however that it was impossible to make 
records of the pressures normally existing in the stems owing 
to the remarkable disturbing influence exerted when a 
manometer was introduced. 
During the hotter and drier parts of the day a slight reduc¬ 
tion in length was sometimes observable. This was always 
small in amount, and usually only just to be detected by the 
method of measurement employed. It never amounted to 
more than 2 or 3 mm. per hour. 
It is thus clearly established that changes of moisture are the 
chief cause of the observed oscillations in the rate of growth of 
the culms of Dendrocalamus. The temperature in the shade 
beneath the clump, where the young growing culms are 
protected during the early part of their growth, shows only 
slight and slow changes. On the other hand when the sun 
is brightly shining the older members of the clump are 
exposed to a much higher temperature, and this, in 
* In another way however light has probably an important, though sub¬ 
sidiary effect. Increased illumination as a rule causes opening of stomata 
and decreased illumination closing of stomata when other conditions are 
unchanged, so that unless Dendrocalamus is quite exceptional in this res¬ 
pect the periodic changes in illumination must co-operate with the nearly 
parallel changes of moisture in inducing corresponding changes in the rate 
of transpiration of the full grown culms, and may thus exert an appreci¬ 
able indirect influence upon the rate of growth of the young Gulms, although 
the direct effect is very small. 
f Ann. Jard. Buit., 2nd Supplement, 1898, p. 30 et. seq. 
