46 FUNCTIONAL INERTIA 



case of extreme insusceptibility. On this point Mr. 

 Robertson writes;* "A more extreme case still is 

 furnished in the winter beds of Hydrocharis. Terras t 

 found that if covered up these buds could be kept 

 in the dormant condition, that is in a condition 

 of (anabolic) inertia for at least two years. To induce 

 germination, heat, light and oxygen were necessary. 

 So great was the inertia that three stimuli of a tonic 

 character were required to elicit a manifestation of 

 irritability, in this case growth. This example forms 

 a transition to the condition of the dry resting seed, 

 which niay be taken as exhibiting the most extreme 

 case of functional inertia. The Hydrocharis pods 

 when dormant are not only living but are giving 

 manifestations of life, inasmuch as they continue to 

 respire to a slight extent throughout their dormant 

 phase (Terras, loc. tit.}. In the dry seed we have an 

 organism that is living, but is affording no indica- 

 tion of life, inasmuch that it does not respire . . . 

 the seed is living although not manifesting life.". . . 

 ' The dry seed may be regarded as an organism whose 

 functional inertia is infinite for any given stimulus, 

 but relatively small for a given combination of 

 stimuli, viz., heat, moisture and oxygen " and light. 

 Here " to elicit that manifestation of irritability 

 which we call growth, and which we take as evidence 

 of life in the seed, three tonic stimuli are necessary." 

 u If we seek in the animal kingdom for cases to 



* R. A. Robertson, " The Latent Life of Plants." Trans. Bot. 

 Soc. Edin, t 1902, p. 187. 



t Terras, Trans. Bot. Soc. Edin., vol. xxi. 1900, p. 318. 



