LIMITING FACTORS TO GROWTH MEASUREMENTS. 363 



that in all these cases, growth in length of shoots takes place 

 in restricted periods which may occur once, twice, or oftener 

 annually, but always with periods of rest intervening. As far 

 as can be seen the climate in Ceylon is favourable to growth 

 almost all the year round and one would perhaps expect that 

 the shoots of a tree would increase in length continuously, 

 since there is only a very short period, the dry season of Feb- 

 ruary and March, when we can see obvious cause for cessation 

 of activity. Instead of this we find a very large number of 

 species which choose a restricted period of 3 or 4 weeks in which 

 to complete all their growth either for the year or for some 

 shorter period, and during the remainder of the time are at 

 rest as far as growth in length is concerned. During the 

 period of rest assimilation is of course going on and the tree 

 stores up reserve materials in its stem, branches, and twigs, 

 and from this supply of reserve the rapid growth of the shorter 

 periods takes place. The reserve is as a rule exhausted by 

 this growth. This growth though rapid in comparison with 

 that of temperate trees is not sufficiently rapid to make possible 

 observations (at any rate unless instruments for magnifying 

 the growth are devised) to show the relation between the 

 growth and the environmental factors. It may however be 

 justifiable to suppose that our general theory of limiting 

 factors is applicable to these cases, and if this is so the theory 

 will be adequate to explain a very large number of growth 



phenomena. 



Cauliflory. 



Another phenomenon which probably has some relation to 

 our theory is that of Cauliflory, so common and so often noted 

 in the tropics. It is well known that stores of reserve food are 

 usually found in trees in the stems and larger branches. 

 Fruits which grow from the main stem or from the larger 

 branches may be expected to grow from these stores of reserve 

 food. It is in fact not unlikely that the biological advantage 

 of cauliflory lies in this very proximity to large stores of 

 reserve. A tree which has its fruits very near to stores of 



