320 Mr. Knight on the Motions , &c. 
conclusion I shall observe, that the sides of the tendrils, where 
in contact with the substance they embraced, were compressed 
and flattened. 
The actions of the tendrils of the pea were so perfectly 
similar to those of the vine, when they came into contact with 
any body, that I need not trouble you with the observations I 
made upon that plant. An increased extension of the cellular 
substance of the bark upon one side of the tendrils, and a cor- 
respondent contraction upon the opposite side, occasioned by 
the operation of light, or the partial pressure of a body in 
contact, appeared in every case, which has come under my 
observation, the obvious cause of the motions of tendrils; and 
therefore, in conformity with the conclusions I drew in my 
last memoir, respecting the growth of roots, I shall venture 
to infer, that they are the result of pure necessity only, unin- 
fluenced by any degrees of sensation, or intellectual powers. 
I am, my dear Sir, 
with much regard, &c. 
THO. ANDREW KNIGHT. 
Downton, April 27, 1812. 
To the Right Hon. Sir Joseph Banks, Bart. K. B. 
