GIANT BAMBOOS. 
249 
determining the course of the grand period of the culm. But 
in the case before us this factor is largely obscured by the 
much larger effect of the length of the growing region. In 
this respect bamboos are probably unique, and cannot, 
strictly speaking, be compared with other plants whose 
growth has been more usually studied. 
In addition to and partly obscuring these periodic changes 
of growth the tables and curves already given show consider¬ 
able oscillations from day to day. The corresponding records 
of rainfall show very clearly that there is a connection 
between the two phenomena. Unfortunately complete 
psychrometric records were not taken, nor indeed was this 
possible in the absence of recording instruments. The 
moisture of the air is however to a large extent proportional 
to rainfall, so that the effects of the two must be dealt with 
together, whereas sunshine and temperature would show an 
almost inverse curve compared with the curve of rainfall. 
It appears therefore that the oscillations from day to day are 
determined almost entirely by conditions of moisture, 
including in this term moisture of the air and of the soil, in 
addition to the direct effect of rain in moistening the leaves 
of the clump and the surfaces of the growing culms them¬ 
selves. The conclusion that changes in atmospheric moisture 
have a large effect was fully borne out by the results of more 
detailed observations made every hour. 
Within certain limits the effect of moisture appeared to be 
greater and more immediate the greater the height which 
had been reached by the culm under observation. This 
effect is very clearly illustrated in pi. XXII., fig. 2. Unfortu¬ 
nately it was impossible to make very accurate hourly 
observations at any great height. The result is probably 
partly due to the more rapid growth, and the larger number 
of internodes concerned in active growth at the greater height ; 
perhaps partly also to the greater distance from the source of 
water which might make the effect of drought more acutely 
felt. At the later stage too the young culm itself possesses 
