48 
Walter Stiles and Ingvar Jorgensen. 
until we have more facts would be premature. Once again we 
would emphasize that what are wanted at present for the solution of 
permeability and related problems are facts. There are already too 
many theories and explanations based on the insufficient data 
available. 
Finally we can scarcely pass over the statement made by Thoday 
in a footnote to his paper, 1 to the effect that we confuse elasticity 
with extensibility. This statement is, we think, unwarranted and mis¬ 
leading. In our paper there was no shadow of doubt whatever as to 
our meaning, and not the least confusion. “ Elasticity ” says 
Professor Love “ is the property of recovery of an original size and 
shape. A body of which the size, or shape, or both size and shape, 
have been altered by the application of forces may, and generally 
does, tend to return to its previous size and shape when the forces 
cease to act. Bodies which exhibit this tendency are said to be 
elastic.” 2 
There appears to us to be nothing in our use of the term 
elasticity which is contradictory to the spirit of the meaning of the 
term as defined above. The first sentence in which we used the 
term was as follows: “ If the cell wall were absolutely elastic the 
intake of water should continue indefinitely.” Thoday 
appears to have misread this expression “absolutely elastic” as 
“ perfectly elastic ” a term with a definite physical meaning. What 
we meant to indicate by the expression “ absolutely elastic ” was the 
condition of a cell wall which was indefinitely extensible and tended 
to return to its original shape. Thoday appears to assume that by 
“absolutely elastic” we meant simply “absolutely extensible.” It 
would be as reasonable to assume that by “ white” we meant “ black” 
and then criticise us for not meaning “ white.” One might regard 
a piece of wax as indefinitely extensible, but no one would ever 
regard it as absolutely elastic. 
In our other sentence in which we used the term we said: “ If 
the cell wall were perfectly inelastic and quite incapable of stretch¬ 
ing ” etc. The meaning of this is perfectly clear and there is no 
scope for confusion. Of course, for a body to be perfectly inelastic 
it is not necessary that it should be incapable of change of shape. 
A piece of plasticene would be practically perfectly inelastic since it 
exhibits no tendency to return to its original shape after deformation. 
But for a body to be elastic, as it is commonly understood, that is, 
to return more or less to its original shape on deformation, we 
generally assume that deformation is possible. 
1 New Phyt., 17, p. 109, 1918. 
1 Encyclopaedia Britannica. 11th Edit., Vol. 9, p. 141, Cambridge, 1910, 
