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different part in each. The writer has seen numerous statements in books, papers and 

 journals in this country, pointing out the necessity of a change in species in renovating a 

 forest, thus applying the rules accepted in agriculture on the authority of Liebeg, for the 

 rotation of crops. Anyone who has had to do with forestry, however, will know that 

 not only is the same species of tree propagated on the same place for centuries, but that, 

 at least with some species, the production increases the longer they are propagated on the 

 same ground. That the foliage falling every year and accumulating does in a degree re- 

 place the manuring and plowing practiced in agriculture, is not the only cause why the 

 same species can grow and be reproduced on the same place for a thousand years, as is 

 the case with extensive beech, fir and spruce forests in Germany. From this experience 

 it would appear that the system of rotation which we see the farmer deems it necessary 

 to apply in the tillage and manuring of his soil, is unnecessary to the forester. 



We shall at once see the reason when we consider the aims of the two. 



The farmer's manipulations tend to increase the soluble inorganic elements of the 

 soil, in order to get the highest yield from his field. He applies his energy to produce 

 the greatest amount of protein compounds and with these to remove the maximum of 

 sulphur and phosphorus. He does not pretend, as does the forester, to raise plants in 

 their natural condition, but only such as have been brought by a continued cultivation to 

 an abnormal state, developing one part to the detriment of another. In Asia, the native 

 country of the wheat, our cereals do not differ in their habitus from the common grass. 

 In Chili, in its native state the potato produces bulbs not larger than a pea, and according 

 to Darwin the yield of one acre would not suffice to sustain for one year the life of one 

 Irish family. It is the abnormal abstraction from the soil of such enormous quantities 

 of mineral constituents for the formation of amylon, gluten, dextrin, sugars, etc., which 

 necessitates the replacing, in the form of manure of these elements', which are taken from 

 the soil with the reaping of the grain, or, since the different plants abstract different 

 quantities and qualities of the different inorganic elements from the soil, calls for a rota- 

 tion of plants. 



The experiments of Pollstorfie Wiegman have beyond doubt demonstrated that the 

 inorganic bases of the soil form an essential factor for the development of all vegetable 

 life, aiid the quantities of the same, as found in the ashes of different plants, may be con- 

 sidered as indicating the amount of these materials needed for their full development. 

 We have said that plants differ in the quantity and in the kind of their mineral ingre- 

 dients very greatly, some of these existing in large quantities and in every soil, others 

 almost entirely lacking in many and only found in small quantities in others. 



Now to make a proportional comparison of plants with regard to the impoverishment 

 of soil, which they severally produce, it is import to determine the kinds and amounts of 

 mineral bases each plant requires. A few results from many analyses by good authori- 

 ties on this point may suffice to show the position of forestry to this question. 



Whilst the percentum of inorganic bases in all kinds of wood scarcely ever exceeds 

 three per cent, and mostly remains below one per cent, of the dry substances, we find the 

 ashes from hay six per cent., wheat and rye straw a little over four per cent., and that 

 from oat chaff not less than eighteen per cent. The farmers reap grain and straw, while 

 the forester, if he consults his own interests, allows twigs and leaves, which contain the 

 gi-eatest part of the inorganic constituents of the tree, to remain on the ground. 



If we compare the amount of mineral substances which are severally removed by a 

 field crop and a timber -growth, we find that a wheat crop abstracts from the same area 

 five times as much inorganic bases as the beech, ten times as much as the pine ; the turnip 

 ten times the amount of the beech and twenty-two times that of the pine. 



From this comparison of well authenticated calculations it would appear that tree- 

 culture has the advantage over agriculture as regards the quantity of inorganic bases 

 required. 



Still more favourably stands the case if we compare them qualitatively. 



The wheat, for instance, yields nearly from one hectare, according to Fresenius, 32.55 

 kilo of potassium, or five times as much as the beech and nearly ten times as much as the 

 pine ; of phosphoric acid 20.31 kilo, which is five times as much as the beech and ten 

 times as much as the pine ; of sulphuric acid 20.58 kilo, that is fifty-seven times as much 



