the Leaves of the Sensitive Plant 



19 



made upon one leaf affects the rest In succession. It is well 

 known that the stem, branches, flowers, and roots of tlie sensi- 

 tive plant have no motion. But M. Desfontaines observed 

 that, on touching the roots with sulphuric acid, the leaves 

 become folded ; and M. Dutrochet obtained a similar result on 

 burning either the flower or the stem. 



If the plant be shaken, all the leaves are simultaneously 

 thrown down, and their leaflets folded. Mr. Lindsay attempted 

 to elucidate the action of the intumescence in raising and 

 depressing the petiole, in the following manner. He cut out 

 a portion from the upper or solar surface of the intumescence ; 

 after which he found that the petiole, upon recovering, rose 

 higher than before, {Fig. 3.) From another leaf he removed 

 the inferior portion of the intumescence : he found, upon this 

 injury, that the leaf declined more than before, and did not 

 again rise, (Fig. 4.) He noticed that a thin slice, pared from 



Fig. 3. 



Fig. 4, 



Fig. 5, 



either surface of the intumescence, has a like effect, but in a 

 less degree than a deep excision : and he found that when 

 similar experiments are made upon the intumescence of the 

 subpetiole, there is no essential difference in the result. 



Thus Mr. Lindsay discovered, that the force which raises 

 the petiole exists in the lower part of the intumescence, and 

 that which depresses it, in the upper. He seems to have con- 

 sidered that the temporary excess of force in either part is 

 produced by an impulsion of the sap from the vessels of the 

 jdelding portion into those of the opposite portion. 



