AN INNER LAW OF ITS ORGANISM. 189 



of its parts, the life of those parts must inevitably and 

 necessarily terminate. This gradually expiring growth at 

 its extremities is, therefore, significant of the fact that the 

 tree has passed its prime, and that its life is gradually 

 drawing to its close. The death of the tree, therefore, 

 takes place from within to without, or from its centre to 

 its circumference, and from ahove to below ; or it dies 

 downwardly, from the extremities of its branches to its 

 roots. 



Schleiden, Gray, De Candolle, and others, have indeed 

 advanced the doctrine that the tree can only perish 

 through storms or other mechanical injuries, and that 

 there is nothing in its organization to intimate that it 

 may not continue to vegetate for an indefinite period of 

 time. But, although we freely admit that it is difficult 

 to point out clearly the several stages of vegetative in- 

 activity, till the life and growth of the whole tree forever 

 ceases, and that in most cases the death of the tree is 

 brought about by violent interruptions to the natural 

 life-processes, or a want of those conditions which are 

 necessary to their continuance, yet we do not altogether 

 agree with the views of these distinguished physiologists, 

 for the reason we have already assigned. 



The growth of the tree in the air, and that of the coral- 

 reef in the ocean, is somewhat analogous. The first is 

 built up by a community of plants, the last by a society 

 of animals ; leaves are the architects in the former, and 

 polypi in the latter instance. Both are equally substan- 

 tial and enduring monuments of the skill of architects 

 alike perishable and insignificant, capable of withstand- 

 ing the storms of the elements from which they draw 

 their life, and which thus rage for hundreds and thou- 

 sands o"f years harmlessly around them. The dead indi- 

 viduals of the coral-reef serve as a firm foundation for 

 succeeding generations of workmen or polypi, who con- 

 tinue their labors at the same structure. So is it with the 

 tree. What is the dead, fissured bark on the outside of 

 yonder old tree-stem, and the dead wood in its inside, but 



