260 PHYSIOLOGY OF TREES. 



zone of cambium to the organisable property of 

 sap, asserts that it is composed of a dilatation of 

 the alburnum. This is a most rational suppo- 

 sition ; because not only agreeable to natural 

 appearances, but also accounting for the fibrous 

 organisation which so soon appears in this new 

 member of the stem. But, unfortunately, this 

 specious conjecture is not true ; because the al- 

 burnum suffers no diminution, but remains ever 

 after of the same form and dimension it had at 

 the end of the last year's growth ; which could 

 not be the case, if any part of its exterior surface 

 was sloughed off to form the new layer. 



Another idea has been entertained respecting 

 the annual growth of the stem, and which ap- 

 pears to be gaining ground, particularly in 

 France. It admits the striking similarity of 

 seeds and buds; and supposes, that as every seed 

 produces roots as well as a stem, so every bud 

 ^produces radicles at the same instant that its 

 leaves, &c. are in progress of development ; 

 which radicles, entering into the then lubrified 

 space between the last year's wood and the bark, 



