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ritability of vegetables proved, to conclude, that be- 

 cause camphor assisted the growth of plants, it acted 

 on their living powers; and it is not right to infer the 

 existence of a property proved in no other way, from 

 the operation of uncertain qualities. 



That camphor may assist the growth of plants it 

 is easy to conceive; and why should we not consider 

 its efficacy as similar to the efficacy of saccharine and 

 mucilaginous matter, and particularly of oils, to which 

 it is nearly allied in composition; and which afford 

 food to the plant, and not stimulus; which are materi- 

 als of assimilation, and not of excitement? 



The arguments in favour of a contraction similar 

 to muscular action have not then much weight; and 

 besides, there are direct facts which render the opinion 

 highly improbable. 



When a single branch of a vine or other tree is 

 introduced in winter into a hot-house, the trunk and 

 the other branches remaining exposed to the cold at- 

 mosphere, the sap will soon begin to move towards the 

 buds in the heated branch; these buds will gradually 

 unfold themselves and begin to transpire; and at length 

 open into leaves. Now if any peculiar contractions of 

 the sap vessels or cells were necessary for the ascent of 

 the sap in the vessels, it is not possible that the applica- 

 tion of heat to a single branch should occasion irrita- 

 ble action to take place in a trunk many feet removed 

 from it, or in roots fixed in the cold soil: but allowing 

 that the energy of heat raises the fluid merely by di- 

 minishing its gravity, increasing the facility of capillary 

 action, and by producing an expansion of the fibres 



