LIMITING FACTORS TO GROWTH MEASUREMENTS. 347 



Take for instance the observations of Shibata (20) on the 

 growth of Phyllostachys mitis in Japan. Here the general con- 

 clusion is that the daily growth is in close agreement with the 

 fluctuations of average daily temperature and has no relation 

 to changes of moisture. Lock's results with Dendrocalamus 

 and Gigantochloa show, on the other hand, a close agreement 

 between humidity and growth and none between temperature 

 and growth. Blackman (2) suggests that, since the tem- 

 perature range atPeradeniya is from 19° C. to 30° C. and that 

 in Japan from 11-6° C. to 20*7° C, we have a clear case of the 

 low temperature being the limiting factor in Japan, while 

 at Peradeniya the higher temperature would admit of more 

 growth than actually takes place, the moisture being the 

 limiting factor. 



The case can, however, scarcely be so simple as this, since 

 my own measurements of Dendrocalamus giganteus at Hak- 

 gala show an extreme temperature range of 9-1° C. to 21-1° C, 

 i.e., almost the same as that in Japan, and yet the growth is 

 found to be in close agreement with the fluctuations of humidity 

 during the day and only to show a relation to temperature 

 during the night. Thus taking the total growth for 24 hours 

 there is no recognisable agreement between the growth and 

 the mean temperature for the period. A day of low humidity 

 will cause quite a slow total growth for the 24 hours compared 

 with a day of rain, even though the average temperatures for 

 the two periods are about the same. Shibata's figures show no 

 such result. The 29th April, for example, was a day of very 

 low humidity, the mean being 43*5 per cent., yet the growth 

 shows a distinct increase in response to the higher temperature, 

 and this is the case on other days also. 



It is quite possible that if more frequent observations had 

 been made by Shibata, reconciliation of the two sets of 

 figures might be supplied. In the absence however of any 

 figures to show the difference between day and night 

 growth in Japan no comparison of the cases can be attempted 

 and the figures must remain outside our generalisation. 



