40 •F THE MEDULLA OR PITH. 



Some considerations have led me to hold 

 a medium opinion between these two ex- 

 tremes. There is, in certain respects, an 

 analogy between the medulla of plants and 

 the nervous system of animals. It is no less 

 assiduously protected than the spinal marrow 

 or principal nerve. It is branched off and 

 diffused through the plant, as nen-es are 

 through the animal. Hence it is not absurd 

 to presume that it may, in like manner, 

 give life and vigour to the whole, though by 

 no means, any more than nerves, the organ 

 or source of nourishment. It is certainly 

 most vigorous and abundant in young and 

 growing branches, and must be supposed to 

 be subservient, in some way or other, to their 

 increase. Mr. Lindsay of Jamaica, in a pa- 

 per read long ago to the Royal Society, but 

 not published, thought he demonstrated the 

 medulla in the leaf-stalk of the Mimosa 

 pudica^ or Sensitive Plant, to be the seat of 

 irritability, nor can I see any thing to invali- 

 date this opinion. 



Mr. Knight, in the Philosophical Transac- 

 tions for 1801, p. 348, supposes the medulla 

 may be a reservoir of moisture, to supply 



