GIANT BAMBOOS. 
263 
Phaseolus supposed the effect to be simply one of turgour, as 
opposed to the other of the two factors to which he ascribes 
changes in the rate of growth, namely, a direct action of the 
protoplasm upon the extensibility of the cell-wall. And 
this seems to be very probably the case in Dendrocalamus as 
well. But it is to be remembered that the control of turgour 
is just as much a function of the living protoplasm as is the 
latter method of control of growth. 
It seems certain that the reaction of changes of moisture 
in the case of the young growing culms of Dendrocalamus 
depends largely upon the transpiration of the adult members 
of the clump. The growing region is so closely covered by 
an impenetrable armour of stout sheathing leaf bases that the 
possibility of a direct action of small changes of atmospheric 
moisture would appear to be quite excluded. The presence 
of this thick and practically opaque covering also probably 
explains the fact that changes of illumination have very 
little effect. We must suppose that transpiration produces 
changes in the pressure of water in the rhizome, and that 
these changes of pressure react upon the turgour of the 
growing cells. 
The rapidity with which this reaction takes place is 
remarkable when we consider the great size of the plant and 
the distance of the foliage of the mature shoots from the 
rhizome and from this to the growing points of the young 
culms. It seems most probable also from this consideration 
that the transmission of the effect must be by changes of 
hydrostatic pressure, and not by any direct conduction of a 
stimulus through living organs. 
Conclusion . 
In the preceding pages some account has been given of a 
preliminary study of the growth of internodes, made in a 
tropical country by the use of the simplest methods only, 
applied to a particular plant of very rapid growth. The result 
of these experiments seems to justify the conclusion that 
