LIMITING FACTORS TO GROWTH MEASUREMENTS. 307 



which the CO 2 supply is in excess and the assimilation is limited 

 by the light. If the light is increased a curve OBE is obtained 

 in which BE is the portion where light is limiting, but allow- 

 ing a higher assimilation than before. A further increase of 

 light gives the curve OCF consisting, as before, of two parts. 

 OC where C0 2 is limiting, and CF where light is limiting. 



In this connection Blackman gives the following axiom : 

 ' When a process is conditioned as to its rapidity by a number 

 of separate factors the rate of the process is limited by the 

 " slowest factor." 



In the case of growth the number of factors is large, and some 

 of them are obscure, but the principal effective conditions of 

 whose action we know something are temperature and supply 

 of water. The most complete sets of measurements of the 

 growth of Bamboos yet taken, those of Lock (12) on Dendro- 

 calamus giganteus; in which the growth showed a close relation 

 to the humidity of the atmosphere, and of Shibata (20) on 

 Phyllostachys mitis, in which the growth was closely related 

 to the temperature, are taken to be examples of the theory of 

 limiting factors. 



At Peradeniya Blackman supposes that, the tempera- 

 ture being high was favourable to growth and would permit 

 more growth than actually took place, the amount of water 

 available being the limiting factor in the growth of the bamboo 

 stems. The temperature in Shibata's experiments was con- 

 siderably lower, and this kept the growth-rate down. The 

 moisture being in excess showed no influence on the growth - 

 rate. 



The three Climates of Ceylon. 



Dendrocalamus giganteus grows in Ceylon in the Botanic- 

 Gardens at Peradeniya, at Hakgala, and at Anuradhapura. 

 These three places are situated respectively in the three differ- 

 ent climatal regions of Ceylon. Peradeniya is at an elevation 

 of 1,500 feet above sea level and has a warm moist climate with 

 only a short dry season in the months of February and March . 

 It gets rain in both the North- East and South- West monsoons, 



