THE SOURCES OF THE XITROGEX OF VEGETATION, ETC. 501 



decomposition of mixtures of nitrogenous and non-nitrogenous substances, in variable 

 proportions, in connexion with soil and water, involves points so highly complicated, 

 that we cannot pretend satisfactorily to answer all the above questions. 



We may, however, ascertain the character of some of the final products of the decom- 

 position, and from a knowledge of these draw conclusions as to the changes of which 

 they are the result under various circumstances. 



Series II. — Experiments on the Decomposition of nitrogenous Organic Matter, made 



ml85& 



The following seiies of experiments was made with a view to embrace a wider range 

 of conditions as to degree of moisture; — to observe the different stages of decomposition 

 as manifested by the odour, &c. ; — to include the circumstances of sprouting, early growth, 

 and subsequent decay of the products of the vegetation ; — and to afford material for a 

 more elaborate inquiry into the character of the products of the decomposition. 



The results given above, in Table VII., do not show any difference between soil and 

 pumice as matrix that we can safely refer to other than incidental causes independent 

 of the action of the matrix itself. Yet we continue the use of the two substances, in 

 order to see if, with a larger percentage of organic matter, and a more complete decom- 

 position, the pumice will retain the ammonia formed as well as the soil. 



About 175 to 200 grammes of soil, or 120 to 150 grammes of pumice, were used as 

 matrix in each experiment, and the other conditions were as follow : — 



{a. 171 seeds, weighing 8-0475 grammes, 50 c. c. water, with ignited Soil. 

 h. 171 seeds, weighing 8*0715 grammes, 100 c. c. water, with ignited Pumice. 

 c. Meal, weighing 9-8810 grammes, 40 c. c. water, with ignited Soil. 



{a. 163 seeds, weighing 8-0440 grammes, 50 c. c. water, with ignited Soil. 

 b. 163 seeds, weighing 8T360 grammes, 100 c. c. water, with ignited Pumice. 

 c. Meal, weighing 8-9670 grammes, 40 c. c. water, with ignited Soil. 



{a. 7 seeds, weighing 6-4700 grammes, 50 c. c. water, with ignited Soil. 

 b. 7 seeds, weighing 5 -7830 grammes, 50 c. c. water, with ignited Pumice. 

 c. Meal, weighing 6T750 grammes, 40 c. c. water, with ignited Soil. 



Those of the mixtures to which about 50 cub. cent, of water were added, were about 

 as moist as soils when in a good condition for vegetable growth. Those with 40 cub. 

 cent, were much drier in appearance, there being no tendency to agglutination of the 

 particles. Those with 100 cub. cent, were very wet, there being some free water above 

 the solid matters. 



The seeds sown with 50 cub. cent, water showed growth in a few days after being 

 put in, and the vessels (B, fig. 8, Plate XII.) were soon filled with a mass of vegetation. 

 Those sown -with double this quantity, or 100 cub. cent, water, showed no indications 

 of sprouting ; and in a few days, the odour evolved from them showed that decompo- 

 sition had set in. The mixtures of meal and soil, also, soon gave odours indicative of 



