86 



LETTERS ON TREES. 



exist only in subordination to animals ; and the objects 

 of their existence are as various as their kinds or 

 species. One is, the formation of organic matter for 

 the use and sustentation of animals. That, indeed, is 

 the first and chief end of their existence, and the only 

 one that need engage our attention here. 



15. Observe: All organic matter comes from the in- 

 organic world — from its water, its air, and its soil ; 

 and sooner or later all organic matter is resolved back 

 again into air, earth, and water. Dust thou art, and 

 unto dust shalt thou return." That is the beginning 

 and the end, the source and destiny of the material 

 part of every hving thing. It is true of animals as it 

 is of vegetables. They are linked corporeally to the 

 dead earth as closely as vegetables are. Equally with 

 vegetables, they are beholden to it for their very 

 fabric, for the materials out of which this is built up 

 and fashioned, and by which it is continually renewed 

 and upheld during its allotted time. 



16. But observe further : Animals require for their 

 sustentation that this inorganic matter shall first have 

 been transformed into organic. They cannot them- 

 selves subsist on inorganic matter as such. Neither 

 have they the power of effecting that transformation 

 for themselves. 



17. Vegetables, however, can do both. Their proper 

 food is carbonic acid, water, and a few simple salts ; 

 and they can so act upon these, and upon ammonia, as 



