LECT. VII.] ANATOMY OF STEMS. 35 1 



to be supposed, from the term deposition of albur- 

 nous matter which Mr. Knight employs, that no- 

 thing more is necessary for the formation of the al- 

 burnum than the deposition of that matter. For 

 although alburnous matter may be justly said to be 

 generated from the sap after its elaboration in the 

 leaf, whether we designate it by the term alburnous 

 matter, or cambium, or proper juice, yet it is merely 

 the pabulum ; the organization of the alburnum, 

 or the transmutation of the cambium into its cel- 

 lular and vascular texture, being the result of the 

 vital principle operating upon it, in a manner which 

 we do not understand, and not of any simple coa- 

 gulation, or attraction, or chemical affinity of its 

 parts, in any way similar to what would take place 

 in the same matter, wherever deposited, if de- 

 prived of vitality. The simple fact, therefore, is, 

 that the sap is changed into proper juice in the 

 leaf, and returned into the bark, where part of it 

 being poured out in a gelatinous form between the 

 liber and the wood, there becomes the raw material 

 from which the new zone of wood, in its state of 

 alburnum, and the new layer of liber, are ma- 

 nufactured by the vital principle inherent in the 

 living plant. 



Such is all that is necessary to be known, in 

 the present stage of our investigation into the 

 origin of the annual zones of wood, by which 

 the diameter of ligneous dicotyledonous plants is 



