LIMITING FACTORS TO GROWTH MEASUREMENTS. 369 



gets very large irregularities of growth which he supposes to 

 be the " Stossweise Aenderungen " of Sachs on a large scale. 

 It is however as a rule in the case of herbaceous plants such as 

 the Dahlia variabilis of Sachs (15) and the Gesnera tubiflora 

 of Baranetzky (1) that such irregular results are obtained. 

 Growth from reserve usually shows some regularity. 



The results of Baranetzky (1) and Sachs (15) on the growth 

 of certain herbaceous stems show a large number of occur- 

 rences of irregularity of growth. These Sachs called "Stossweise 

 Aenderungen " and attributed them to something inherent 

 in the plant itself and independent of external conditions. 

 They do indeed in some cases seem so large and so irregular as 

 to preclude dependence upon the fairly constant conditions 

 of the laboratory in which the experiments were carried on. 

 It may be however that even these could be accounted for by 

 the supposition that several different factors out of the many 

 on winch growth depends became limiting in turn for shorter 

 or longer periods. In the case of plants under open air con- 

 ditions when aU the external factors concerned are liable to 

 considerable variations and irregularities, it is even more 

 probable that the irregularities of the growth curves could be 

 explained on these lines. 



It seems therefore probable that our theory will be adequate 

 to account for cases of growth where no reserves have been 

 stored as well as for cases of undoubted growth from reserve. 

 The fact that there may possibly be no sharp dividing line 

 between the cases of growth from reserve and of growth with- 

 out reserve does not at all invalidate the above reasoning. 



VI.— BIOLOGICAL ADVANTAGE OF RESERVE . 

 FOOD STORES. 



The biological advantage of the formation of large stores 

 of reserve does not seem clear in the case of climates like 

 Ceylon where growth conditions are favourable nearly all the 

 year round. It is to be remembered however that there is 



9(8)06 (35) 



