INFLUENCE OF EXTERNAL CONDITIONS ON GROWTH 



27s 



the last both in terms of grams and in atmospheres. The total pressure divided 

 by the cross-sectional area of the root is of course the pressure per square 

 millimeter. The last value is then divided by 10.33 (the weight, in grams, of 

 a mercury column 760 mm. high and with a cross-section of i sq. mm.), to give 

 the pressure in atmospheres. 



From these data it appears that the root of the Windsor bean {Vicia faba) 

 may develop a downward pressure of from 226 to 352 g., or that it may exert a 

 pressure of from 5 to 19 atmospheres. 



