LETTER IV. 



The growth of one year is only subservient to the circulation of 

 the next, and is ever afterwards of use merely in giving strength 

 and stability to the trunk, in order to support the increasing size 

 and weight of the branches and leaves." — Dr John Ware. 



June 30, 1854. 



My Dear Sons, 



1. To proceed with the exposition of my theory. I 

 have said that the dead stems and roots of the plants 

 of this year serve to the plants of next year both the 

 purpose of a soil and the purpose of a support, or of a 

 framework, or scaffolding ; that the former is for a 

 time only, the latter for all time — the one purpose 

 being temporary, the other permanent as the tree 

 itself; and likewise, that the living plants of this year 

 grow parasitically at the extremities of, and also either 

 around or within, the dead stems and roots of the 

 plants of last year. Possibly you may have difficulty 

 in comprehending what all this means. I will endea- 

 vour to make my meaning plain. 



2. Trees, you know, are divided by botanists into 

 two great classes, the Exogens and the Endogens. 



