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special productions of certain peculiar plants aud sometimes of particular 

 organs in those plants. Second, those substances which are always found 

 present in all vegetable life and which make up a greater part of the solid 

 portion of every tree or plant. With the latter division we are to deal and 

 for our purpose we will consider it under two heads; first, those organic 

 constituents that are found in all trees and shrubs during their growth, 

 and second, those mineral constituents that remain after the combustion 

 of the wood of the plant. The organic constituents wei-e always held to 

 be necessary to the growth of the tree while the inorganic, since they var- 

 ied with the nature of the soil, were thought to bq accidental, but this 

 idea has long since vanished and now the mineral constituents are recog- 

 nized as being of the first importance to the vegetable world. 



Prof. Liebig has said "every vegetable requires for its fullest develop- 

 ment and the fulfillment of its vital functions the presence of certain or- 

 ganic acids, of the use of which, however, we are ignorant, but farther it 

 also requires that these acids be in union with a base." 



It appears from experiment that such substances as (Na^o) j (^K^ o^) *°*^ 

 (""^M^o^'^) ^^^^ ^^ ^ certain extent, act as substitutes for each other, but if 

 it so happens that the supply from the ground is insufficient for the pur- 

 pose of the tree it cannot thrive imless it has the power of secreting an 

 organic base for its own use, and with trees this is seldom possible. Prof. 

 Liebig further shows that a certain degree of consistency attends the quan- 

 tity of bases in combination with organic acids present in the same plant 

 grown on different soils, although the proportion of bases may of them- 

 selves be very different. An analysis of two pine trees grown under very 

 different conditions showed the quantity of oxygen present in the carbo- 

 nate to be nearly the same, thus proving that the proportional quantities 

 of organic acids in the two trees must have been united with equivalent 

 quantities of bases. The same was also observed in two fir trees, one of 

 which was grown in Norway and the other in France. The question now 

 arises. Is each of the mineral constituents present in the tree essential to 

 its development? Stohmann has shown by direct experiment that all the 

 mineral food elements have an independent value to the growth of the 

 tree. Potash can not take the place of soda, nor can calcium take that 

 of magnesium. Though they are all necessary for the growth of the tree, 

 for it has been shown conclusively by experimental investigation that the 

 growth of a tree is a function of its mineral food elements, they do not all 

 have an equal value as factors of nutrition. The growth of a tree would 



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