:.;, CHAPTER III. 



THE INNER ORGANIZATION OP TREES, OR A DESCRIPTION OP THE 

 ANATOMY AND PHYSIOLOGY OF THE DIFFERENT SPECIES OP 

 CELLS WHICH ENTER INTO THE COMPOSITION OF THEIR TISSUES. 



IF we wish to recognize the law according to which the 

 tree is built up out of its parts as a compound harmonious 

 whole, we must first resolve the representation of the whole 

 into that unit which lies at the foundation of its super- 

 structure. This we have already done, to some extent, in 

 the two previous chapters. Taking the tree, in the most 

 extended signification of the term, as a separate individual 

 or unit with reference to a forest, we have shown that this 

 individual tree consists of a number of individual plants of 

 a highly composite character called branches, which differ 

 from the entire tree itself only in the smaller scale on 

 which they are constructed, and which actually prefigure the 

 amount of growth of that tree at an earlier stage of its life. 

 These branches are formed by a union of yet simpler indi- 

 viduals called shoots, and the shoots themselves are built up 

 by phytons or leaves, individuals or units which rank still 

 lower in the series. In this manner we have been led to the 

 leaf as the fundamental organ in the building up of the 

 tree-form. 



But this analysis may be carried much further. It may 

 be applied to the inner organization of the tree. Thus the 

 axis or stem separates into two distinct systems, the bark 

 and the wood, as the two highest units of its anatomical 

 composition. Each of these systems again resolves itself 

 into a repetition of single annual layers. If we examine 



