64 THE CONICAL GROWTH OF TREES. 



cessive annual growths in length made by the principal 

 axis ; for in this case quite another result is obtained, that 

 axis having hardly grown at all after the sixteenth year. 

 The three broad wood-rings last formed must therefore 

 have derived their matter from the branches, and we find 

 on examining the side axes, which are thirty-three in 

 number, that eleven of them, formed the last three years, 

 are the most developed ; to these is therefore to be attri- 

 buted the three broad wood-rings. 



The above investigations would seem to lead irresistibly 

 to the conclusion, that the breadth of the wood-rings is 

 determined not only by the activity of the leaves of the 

 terminal shoot of the axis, but that the leaves of the side 

 axes, or of the whole system of axes, co-operate, and there- 

 fore that the leafage of each season forms a common source, 

 whence is derived not only the nutriment forming the new 

 layer or covering of each individual branch or system of 

 axes, but of the main axis or support of the whole of them 

 the stem. For not only each leaf, but each twig, branch- 

 let, and branch contributes its part, during the season of 

 vegetative activity, to the formation of this new conical 

 layer or woody mantle, with which the tree is annually re- 

 clothed from the tops of its branches to the extremities of 

 its roots, a new garment of unity, so to speak. 



A clear conception of the entire process of this annual 

 renovation, can only be obtained by giving due prominence 

 to the fact, that the growth and life of the tree after the 

 first year is entirely superficial, and totally confined to the 

 forming stratum of new bark and wood. The bark and 

 wood-cells constituting the growth of each year, die when 

 their vital activity ceases in the Fall. There is no renewal 

 of their life on the return of Spring ; for, as we have al- 

 ready stated on page 44, " So soon as a cell ceases to form 

 new cells, or to develope and carry nourishing matter, so 

 soon as its fluid contents disappear and it becomes filled 

 with air, it maybe considered as dead." Now, this is pre- 

 cisely the condition of the duct-cells, and to a certain ex- 

 tent of the fibre-cells, at the end of the first year. They 

 are fully formed the first year, and when the life of the 



