GIANT BAMBOOS. 
255 
periodicity, not exactly corresponding with that of rate of 
growth, but still showing some agreement. 
The periodicity in the final length of the internodes 
themselves must also have some influence, if only a small 
one, upon the grand period of growth of a culm taken as a 
-whole. I have already mentioned certain abnormalities in 
this period which are apparently to be associated with 
external injuries and pressures. But the final period of 
length of intemodes is usually very regular, and this would 
seem to indicate that certain irregularities of length in the 
young intemodes, as observed in longitudinal section of the 
bud, are more or less fully compensated for as growth 
-continues. 
It may be supposed that the external meteorological 
| conditions, of which moisture is the only one here closely 
examined, affects chiefly the turgour and rate of elongation 
of the individual growing cells of the intemodes. To what 
extent and in what way the other factors here enumerated 
affect the result it seems impossible to say in the present 
state of knowledge of the subject. 
4 .—The Effect of Changes of Moisture upon the Growth of 
It is remarkable that so little attention has hitherto been 
paid to the reaction of the growth of plants to changes of 
moisture. Pfeffer* connects the fact that light has much 
more influence than temperature upon the form of plants 
with the greater importance of light in the economy of the 
plant. Moisture, however, is an even more necessary 
condition for the growth of plants than light itself, since 
growth can take place in darkness, but not in the absence 
of moisture. Nevertheless the effects of light and of 
temperature have been closely studied by physiologists, but 
the effect of moisture much less fully. 
! Pftanzenphysiologie Bd. 2, p. J 
