254 LOCK: THE GROWTH OP 
the factors upon which the course of elongation of the 
culms depends, it may yet be worth while to enumerate 
some of the circumstances which would make any such 
elucidation a matter of great complexity. 
As has been already stated, the course of the grand period 
of growth of the culm regarded as a whole must depend 
very largely upon the total length of the growing region at 
various stages. And in this connection it is to be remembered 
that the elongation of the older internodes takes place at an 
intercalary region of growth at the base of each intemode, 
at which point elongation continues after the upper part of 
the intemode has ceased to grow in length. In speaking of 
the growing region then, I here mean to imply the whole 
section of the culm situated between its apex and the base 
of the lowest growing intemode. In the earlier stages this 
region is short and growth is slow. Later on, as the region 
of active growth becomes longer, the rate of elongation 
rapidly increases, and during the middle period of rapid 
growth the lowest growing internode may be more than 5 
metres from the growing point. Later on the region of 
growth is shorter and growth becomes slower. 
When the bud begins to elongate a very large number of 
internodes are already laid down in it. The formation 
of new internodes continues during the elongation of the 
culm; but in the later stages of elongation, the number of 
young interaodes enclosed in the bud is small. It follows 
therefore that at first new leaves unfold and new internodes 
take on their most rapid phase of elongation at a shorter 
interval than that between the formation of new internodes 
at the growing point. 
The leaves moreover were observed to unfold at a 
gradually increasing interval of time, this interval being 
about 24 hours when the culms were 2-3 metres high, and 
gradually becoming longer as the height increased. At 
the earlier stages of development of the bud this interval 
must also have been longer, so that we have here another 
