LIMITING FACTORS TO GROWTH MEASUREMENTS. 309 



The average humidity for both months is 77 per cent. Thus , 

 speaking broadly, Peradeniya may be said to have a warm, 

 moist climate, Hakgala a cool, moist climate, and Anuradha- 

 pura a hot and rather dry climate. 



Kandy, where some of the measurements of Furcrcea were 

 taken, is four miles from Peradeniya, and resembles it closely in 

 climate. It is subject to slightly greater extremes of temper- 

 ature. 



There seemed therefore to be a good opportunity to take 

 measurements of the growth of Dendrocalamus through a 

 large range of temperature and under widely different con- 

 ditions of water supply, and under these conditions it seemed 

 possible that a decisive test of the Theory of Limiting Factors 

 could be obtained. 



Since the climate of Ceylon is so favourable to growth, other 

 examples of very rapid growth are to be obtained, and it has 

 been possible in the case of some other species, notably in the 

 case of the inflorescence axis of Agave and Furcrcea, to obtain 

 evidence which further tests the theory. 



The present paper is mainly concerned with cases of growth 

 from a large store of reserve food material, not only because 

 it is usually in these cases that the fastest growth takes place , 

 but also because here the problem of growth is theoretically 

 much simpler. Such growth once started only implies the 

 transference of a certain amount of highly-organized material 

 from one part of the plant to another, and the elaboration of 

 this material to a higher stage of complexity. All the supplies 

 both of organic and mineral food, and often of water too, 

 are contained within the plant. In other cases the growth 

 depends on material which has to be worked up from the 

 simple form of oxygen and carbon-dioxide, and the pro- 

 vision of a sufficient supply of food to the growing organ 

 involves conditions favourable not merely to the elabora- 

 tion and transference of such a highly- organized material as 

 starch, but also to the processes of assimilation and trans- 

 piration. 



