376 CONSERVATIVE ORGANS. [LECT. VII. 



sorium of its own ||, could not be supported un- 

 der such a circumstance, did any analogy exist 

 between the medulla of plants and the spinal 

 marrow of animals. Grew and Malpighi believed 

 that the functions <jf the pith are the same as those 

 of the cellular integument, which they regarded 

 as the organ for elaborating the sap into nourish- 

 ment for the support of the plant, and to give 

 origin to future buds; an opinion which Mr. 

 Keith regards as the best founded of any yet ad- 

 vanced, with the exception of that part of it 

 which relates to the origin of buds. Du Hamel, on 

 the contrary, considered the pith in common with 

 the general cellular texture, as merely intended to 

 hold together the various parts of the plant ; and 

 lastly, Mr. Knight has supposed that " it forms a 

 66 reservoir to supply the leaf with moisture, when- 

 " ever an excess of perspiration puts that in a 

 " state to require it ;." There is certainly much 

 plausibility in Mr. Knight's suggestion ; and it is 

 not, in my opinion, destroyed, as has been sup- 



|| " The pith,'' says Darwin, " communicates to the leaves 

 " on each side of it, but not to the new buds in the bosoms of 

 " those leaves ; because those new buds are each an indi- 

 " vidual being, generated by the caudex of the leaf, and must, 

 " therefore, possess a sensorium of its own.'* Phytologia, 

 xviii. 2, 13. 



| Phil. Trans. 1803, p. 349. A similar opinion is advanced 

 by Plenck, in his Physiologia Plantarum. 



