STEPHEN HALES 129 



the precipitated moisture, the well-known plan 

 followed by various French observers. 



He (Vegetable Staticks, p. sO concluded his 

 balance of loss and gain in transpiring plants by 

 estimating the amount of available water in the 

 soil to a depth of three feet, and calculating how 

 long his sunflower would exist without watering. 

 He further concludes (p. 57) that an annual rainfall 

 of 22 inches is "sufficient for all the purposes of 

 nature, in such flat countries as this about Tedding- 

 ton." 



He constantly notes small points of interest, 

 e.g. (p. 82) that with cut branches the water ab- 

 sorbed diminishes each day, and that the former 

 vigour of absorption may be partly renewed by 

 cut ti na fresh surface.^ 



He also showed (p. 89) that the transpiration 

 current can flow perfectly well from apex to base 

 when the apical end is immersed in water. 



These are familiar facts to us, but we should 

 realise that it is to the industry and ingenuity of 

 Hales that we owe them. In a repetition (p. 90) 

 of the last experiment we have the first mention 

 of a fact fundamentally important. He took two 

 branches (which with a clerical touch he calls M 

 and N), and having removed the bark from a part 

 of the branch, dipped the ends in water, iV with the 

 great end downwards but M upside down. In this 

 way he showed that the bark was not necessary for 

 the absorpltion or transmission of water.^ I suspect 



• Compare F. von Hohnel, Bot. Zeitung, 1879, p. 318. 



' This is also shown by experiment xc, Vegetable Staticks, p. 123. 



