354 CONSERVATIVE ORGANS. [LECT. VII. 



with two or more cotyledons, are to be regarded 

 as fully established : 



1. That the proper juice descending from the 

 leaf through the vessels of the bark, and poured 

 out between it and the wood of the preceding 

 year, is the material from which the new wood or 

 alburnum is formed. 



2. That the organic power, or vital principle, 

 inherent in the plant, transforms this viscous 

 fluid into cells or vessels, or regularly organized 

 alburnum ; the divergent layers being formed at 

 the same time as the vertical or concentric layers. 



3. That under certain circumstances, such as 

 the entire decortication of a stem, the lateral com- 

 munications, which exist throughout the vegetable 

 structure, may conduct the descending juices 

 through the wood, so as to be thrown out in 

 detached spots on its surface ; and there be trans- 

 formed into new bark and alburnum. 



The use of the wood to the plant, exclusive of 

 its power of supporting and elevating the buds 

 with their leaves and fructification in the atmo- 

 sphere, is chiefly confined to its soft or alburnous 

 state. In this state it is endowed with a high 

 degree of irritability. But if it be freely exposed 

 to the atmosphere during a few hours only, all 

 vegetation for ever ceases on that surface ; and, 

 although the bark may close above it, and new 

 wood be formed over it, yet, no vital union 



