Laivs of Fluctuations 721 



the following day the weather may be unfavor- 

 able and greatly retard growth. The individual 

 differences seem to be due, at least in a very 

 great measure, to such apparent trifles. 



On the other hand partial differences are 

 often manifestly due to similar causes. Con- 

 sidering the various stems of plants, which mul- 

 tiply themselves by runners or by buds on the 

 roots, the assertion is in no need of further 

 proof. The same holds good for all cases of 

 artificial multiplication by cuttings, or by other 

 vegetative methods. But even if we limit our- 

 selves to the leaves of a single tree, or the 

 branches of a shrub, or the flowers on a plant, 

 the same rule prevails. The development of 

 the leaves is dependent on their position, wheth- 

 er inserted on strong or weak branches, exposed 

 to more or less light, or nourished by strong or 

 weak roots. The vigor of the axillary buds 

 and of the branches which they may produce is 

 dependent upon the growth and activity of the 

 leaves to which the buds are axillary. 



This dependency on local nutrition leads to 

 the general law of periodicity, which, broadly 

 speaking, governs the occurrence of the fluctuat- 

 ing deviations of the organs. This law of pe- 

 riodicity involves the general principle that 

 every axis, as a rule, increases in strength when 



