490 ORGANOLOGY. 



dependence of the produce of nitrogenous compounds of the manure. 

 The production increases as fixed alkalies and organic salts are present, 

 and still more as the salts of phosphoric acid are brought into action. 



From the preceding we learn, that wild plants produce these nitroge- 

 nous compounds independently of the organic nitrogenous matters held 

 in the soil, and of all forms of ammonia not proceeding from the atmo- 

 sphere* ; and this makes it at least in the highest degree probable that 

 the same law holds good for cultivated plants. 



3. Phosphorus and Sulphur. The phosphorus and sulphur held in 

 combination with the elements containing nitrogen are very insignificant. 

 If we reckon all nitrogen as albumen, and take the highest produce of 

 nitrogen which occurs, as in peas, we obtain about 2 Ibs. of sulphur and 

 1 Ib. of phosphorus as the produce of each acre of land in the year ; that 

 is, the soil, taken at 12 inches deep, must produce in the course of the 

 year, in 434 Ibs. of earth, one grain of sulphur and half a grain of phos- 

 phorus. Every 434 Ibs. of earth corresponds to a surface of almost three 

 square feet. Now, supposing that this phosphorus and sulphur arises 

 from sulphuretted and phosphuretted hydrogen, whereby the improbable 

 hypothesis of the decomposition of sulphates and phosphates is avoided, 

 then we must assume that the earth, during a period of vegetation of 

 120 days, absorbs within twenty-four hours from an air-pillar of three 

 square feet of surface of the soil, 0*0088 grains of sulphuretted hydrogen, 

 and 0-0046 of phosphuretted hydrogen, f Now, if we take only 3000 

 cubic feet of air as entering into the calculation, then the cubic foot of 

 air would need to contain only -gu^V^nj^ f a g ra i n of sulphuretted hydro- 

 gen, and inroVrroth f a grain of phosphuretted hydrogen, in order to suffice 

 to the total demands of vegetation. No person will attempt to prove 

 the absence of this quantity in the air, and the possibility of its existence 

 arises from the many processes of putrefaction, by which phosphuretted 

 and sulphuretted hydrogen is delivered ; and to these must be added vol- 

 canic processes, such as sulphureous springs, which give out quantities of 

 sulphuretted hydrogen, and probably also of phosphuretted hydrogen, 

 into the air. However, we may well lay aside the consideration of these 

 minimal quantities, since questions of more importance demand our 

 attention. 



192. The vegetable world in general receives its organic 

 elements through carbonic acid, salts of ammonia, and water ; this is 

 probably sufficient for all the tribes of plants excepting the true 

 parasites. Yet we cannot maintain that plants growing in a moor 

 soil may not also need organic nourishment. Nutrition through 

 inorganic compounds serves only for plants with roots, and in 

 these only for the root-cells ; all other cells those which exist in 

 branches, buds, and embryos, in connection with the mother plant, 

 are nourished exclusively upon matters already more or less 

 assimilated. 



* Whether this exists already in the atmosphere, or has been produced by the process 

 of decay in contact with nitrogen. 



f Peas, which of all cultivated plants contain the largest quantity of nitrogenous 

 matters, yield somewhat more than 50 Ibs. of nitrogen on an acre. In albumen, accord- 

 ing to Mulder, there are 15-83 of nitrogen, 0'68 of sulphur, and 0'33 of phosphorus. 

 If we take the most exorbitant case, that of Lucerne, we should have at the utmost in a 

 cubic foot, the Y^gth of a grain of sulphuretted hydrogen, and jgg^th of a grain of 

 phosphuretted hydrogen. 



