FUNCTIONAL INERTIA AS LATENT PERIODS, &c. 45 



appointed period of life/' These things cannot 

 be due to affectability. 



At my suggestion, my colleague, Mr. R. A. Robert- 

 son, looked for examples of functional inertia in 

 vegetable protoplasm to find them as widely dis- 

 tributed as those of affectability. Thus, writing of 

 plant-rhythms, Mr. Robertson says : * " The post- 

 stimulant continuance of periodicity of growth or of 

 movement the opening or closing of flowers, move- 

 ments of leaves whether diurnal or seasonal is to be 

 credited to this property of functional inertia. Thus 

 the periodicity of growth induced by the alternation 

 of day and night is retained for a time in continuous 

 darkness, and seasonal periodicity is exhibited by 

 deciduous trees when removed to countries where 

 the vegetation is ever-green, while in cases of experi- 

 mentally induced periodicity, the periodicity con- 

 tinues for a time after the stimuli are withdrawn. 

 All these are examples of the katabolic phase of the 

 inertia. For particular cases the time- value of the 

 inertia varies : thus the diurnal periodicity is lost 

 after two days by some plants, while it is retained for 

 as much as two weeks by others. The latter have 

 relatively more inertia than the former. Seasonal 

 periodicity exhibits similar variations, and in the 

 practical horticultural operations of forcing and cold 

 storage, we see the property under other aspects. " 



The condition of latent life of plants is a notable 



* R. A. Robertson, " The Functional Inertia of Plant Proto- 

 plasm," Proc. Roy. Soc. Edin., Session 1901-1902, vol. xxvi. 

 Part iii. 



