Thiiininor and Pninino Forest Trees. 



s 



It is well known that all vegetables take in their li(|ULd food 

 mainly from the soil, and their gaseous supply chiefly from the atmo- 

 sphere ; and though some of their inorganic elements are derived 

 immediately from the soil, carbon, which forms one-half the weight 

 and nearl}^ the whole bulk of the tree, is obtained directly from the 

 atmosphere through the pores of the leaves. 



Chemistry proves beyond a doubt that over equal areas in the same 

 latitude, wliich necessarily receive equal amounts of light and lieatj 

 similar quantities of carbon are obtained from the atmosphere by the 

 crop of vegetntion,. whether it consist of the lofty forest trees, or the 

 lowly and almost recumbent clovers or grasses ; and since weeds 

 which are indigenous to the soil are so much more rapid in their 

 growth than the cultivated plants, they must obtain the largest share 

 of this vegetable food — a strong argument in favour of clean cultiva- 

 tion, whether in the nursery, garden, plantation, or upon the farm. 



The careful analysis of an ordinary piece of wood which has been 

 dried at a temperature of 212 degrees proves that one-half its weight 

 consists of charcoal, which is again subdivided into carbon, and from 

 one to five per cent, of ashes or inorganic matter. These ashes are 

 made up of lime, potash, and a few other ingredients. Every 100 

 parts of atmospheric air contain about twenty of oxygen and eighty 

 of azote, which latter merely acts as a diluter of the oxygen. Car- 

 bonic acid gas is present in the proportion of one in 2,500. This 

 carbonic acid is composed of one of carbon, combined with two and 

 two-thirds its Aveight of oxygen, and is decomposed by the leaves under 

 the action of light, the leaves retaining the carbon and giving off the 

 oxygen. During the night, however, the process is reversed, as the 

 leaves then absorb oxygen and give off carbon, though in very small 

 quantities. This will account for the great rapidity of growth of 

 vegetation in those latitudes where the sun never sets for weeks and 

 months together, the continual absorption of carbon forcing it on 

 very rapidly. By the decomposition of ammonia plants obtain their 

 nitrogen. 



Johnson, in his " Elements of Agricultural Chemistry," tells us that 

 upon lands of average fertility, from one-third to four-fifths of the 

 entire amount of carbon contained in the crop is obtained from the 

 air ; and that to catch the small amount of carbonic acid " the tree 

 hangs out thousands of square feet of leaf, in perpetual motion 

 through an ever-moving air, and thus by the conjoined labours of 

 millions of pores the sul)3tance of whole forests of solid wood are 

 slowly extracted from the fleeting winds." The same authority also 

 tells us that upon a square inch of surface of the common lilac leaf 

 120,000 of these pores have been counted, and upon an oak tree 

 7,000,000 of leaves. 



VOL. I. • 7, 



