248 LOCK : THE GROWTH OP 
The observations recorded show that the culms of the 
giant bamboo pass through a definite grand period of growth. 
At first, when the bud is just appearing above grpund, 
elongation is slow. Soon,however,a rapidincrease intherate 
of growth sets in, and is continued until a height of some 5 
metres has been attained. For the next 10 metres or more, 
growth, apart from oscillations which can be ascribed to the 
effect of external conditions, appears to remain fairly steady. 
Later on the rate of elongation falls gradually and finally 
becomes very slow. This slow growth is continued for a 
considerable time at the apex of the halm. 
If now a cause of this phenomenon be sought, it may 
be found at once in the var ying length of the growing 
region. Up to a height of nearly 5 metres the intercalary 
growing areas are spread over almost the whole length of the 
young culm. And we should therefore perhaps expect 
growth to be proportionate to length. But at the earlier 
stages a larger proportion of the young culm, then less 
than half a metre high, is in the embryonic phase of growth, 
and consequently elongation is proportionately slower. 
When a length of something over 5 metres has been reached, 
the older internodes at the base of the culm gradually 
cease to elongate. The growing region is thus kept at 
approximately the same length, and growth also remains 
nearly constant. As the end of the growing period is 
approached it appears certain that reduction in length of the 
growing region must be accompanied by a steady falling off 
in the growth of the culm regarded as a whole, until the 
adult length is reached and growth ceases altogether. It 
was not found possible to make any trustworthy observations 
at this final period. Neither could observations be made 
upon the growth of individual internodes, since these are 
completely covered by the sheathing bases of the leaves 
until their growth is very nearly completed. 
The rate of elongation of the various developing cells at 
different stages of growth also doubtless plays a part in 
