SECT. I. WOUNDS. 47Q 



the under surface of the earth contained in the bar- 

 rel, with the top pointing downwards, did not 

 vegetate. Hence he concluded that germes both 

 of the root and branch are dispersed throughout the 

 whole of the plant, and are developed as the exi- 

 gency of the case requires.* 



Others less prodigal of germes think that the 

 buds are regenerated only from the plexus of the 

 vessels of the inner bark ; perhaps, because it is 

 from the inner bark that the union of the graft and 

 stock is effected. But Mr. Knight thinks he has dis- 

 covered the true source of the regeneration of buds 

 in the proper juice that is lodged in the alburnum. 

 This conjecture is supported by the following facts : 



If the stalk of Crambe maritima is cut off near 

 the ground in the spring, the pith within that part 

 of the stalk which remains still attached to the root 

 rots, and a cup is formed that collects water in the 

 succeeding winter. The sides of the cup consist of 

 a woody substance which resembles the alburnum 

 of trees, and new buds are often seen in the follow- 

 ing spring to be protruded from within the cup. 



Buds were also observed to be generated on the 

 sections formed by the knife in separating Potatoes 

 into cuttings, and were in many instances elongated 

 into runners, which gave origin to other tubers. 

 Now the Potatoe, says Mr. Knight, consists of four 

 distinct parts ; the epidermis, true skin, bark, and in- 

 ternal mass, which he denominates an alburnum, 

 * Phys. des Arbres, liv. iv. chap. v. 



