58 TRANSACTIONS OF THE ILLINOIS 



water, and the atmosphere being charged with moisture above — these two 

 things will quickly show any one why that country is damper in its 

 atmosphere and surface than it would be without that forest. 



Now let us go on downward. Some rain falls on that forest, and 

 some finds its way to this spongy mass of earth, and is retained for a 

 while, and gradually goes down, down, down. You may say that the 

 moisture passes into the roots of trees so much that it leaves the soil dry. 

 How does it get into the roots of trees ? There is a principle involved 

 there — a very fine one, too. The roots are not open mouths, sucking up 

 moisture out of the earth ; they are closed cells, with no opening to be 

 seen in them, and the moisture that passes into them passes in on the 

 principle of osmose absorption, and that tree will not remain turgid, 

 and in the highest condition of health, unless there is moisture in the 

 earth to absorb. That osmose absorption ceases, to a certain extent, 

 whenever the amount of moisture falls below a certain point. We can 

 find forests in such a condition that in many places the soil is powder 

 dry. These are suffering for want of moisture ; and if you ever dig 

 down into the forest, and find the soil dry and dusty where the roots are, 

 that forest is suffering. 



Under these circumstances, just one thing must happen — the moist- 

 ure which goes into these trees, and which is essential to their healthy 

 growth, and even life, must ultimately all come from the atmosphere. 

 Whether the tree takes it from the earth through the absorbing root sur- 

 face, or directly from the air through leaves and bark, it still must come . 

 from the air as rain or dew, or as invisible gas. 



And as the presence of these trees necessitates a greater supply of 

 moisture from the air than would be necessary for an herbage crop, so if 

 trees live and thrive, their very existence proves that a larger sum of 

 moisture is being deposited from the atmosphere at that point than would 

 be deposited were they absent. 



The remark has been made that vegetation does not fix water. Surely 

 this is an error. The growing plant is but a laboratory, wherein the inor- 

 ganic simples are worked over into organic compounds, or where the 

 inorganic compounds are broken up and recombined under the domi- 

 nance of that mysterious principle — the vital force. Trees are making 

 cellulose, lignine, starch, sugar, oil, resins, gums, etc., in which are the 

 elements carbon, hydrogen and oxygen. The carbon is derived from the 

 carbonic acid gas of the atmosphere, while the hydrogen and the oxygen 

 come mainly from the water. Here, then, in the wood, bark, and the 

 various products of the vegetative function, the tree has been fixing 



