Me&idts of Experiments on Permanent Grass-lancl. 331 



acid in the vegetable substance before incineration. The conclusion 

 was that, independently of any specially physiological function of the 

 bases, such as that of potash in connection with the formation of 

 carbohydrates, for example, their office was prominently also that of 

 carriers of nitric acid, and that when the nitrogen had been assimilated, 

 the base was left as a residue in combination with organic acid — which 

 was represented by carbonic acid in the ash. Further existing knowledge 

 — as to the condition in which combined nitrogen is found in soil waters, 

 as to the action of nitrates used as manures, as to the presence of 

 nitrates in still-growing plants, and as to the connection between the 

 nitrogen assimilated and the composition of the ash as had been illus- 

 trated — pointed to the conclusion that, at any rate a large amount of 

 the nitrogen of the chlorophyllous vegetation on the earth's surface was 

 derived from nitrates ; whilst, so far as this was the case, the raison 

 d'Mre of much of the fixed base found in the ashes of plants would 

 seem to be clearly indicated. 



The various results and conclusions above referred to were found to 

 afford material aid in the interpretation of the differences in the 

 chemical composition of the mixed herbage of the different plots which 

 was next considered, so far as the first crops over the first twenty 

 years were concerned. 



For the purposes of the illustrations the differently manured plots 

 were arranged in four groups as follows : — 1. Plots without manure or 

 with farmyard manure. 2. Plots with nitrogenous manures alone. 

 3. Plots with mineral manures alone. 4. Plots with nitrogenous and 

 mineral manures together. Average results for each plot, generally 

 for a period of eighteen years, 1856 — 1873, and including the per- 

 centages of nitrogen, crude ash, and pure ash, in the dry substance of 

 the produce ; also the percentage composition of the pure ash were 

 brought together in a table, and are discussed in detail. The close 

 dependence of the chemical composition of the mixed herbage on its 

 botanical composition, and on the character of development of the 

 plants, was throughout illustrated. It was further shown, that the 

 mineral composition of the mixed herbage was very directly dependent 

 on the supplies available to the plant within the soil. Indeed, when it 

 was considered that the mixed herbage of permanent grass land 

 includes plants of very various root-range and root-habit, and that 

 some of them vegetate more or less almost the year round, it was not 

 surprising to find that the composition of the produce was, upon the 

 whole, a somewhat close reflection of the available supplies within the 

 range of the roots. It was, in fact, much more so than in the case of 

 individual crops grown separately. Within certain limits, this was the 

 case even with the constituents of, so to speak, less functional im- 

 portance than those which more obviously determined the description 

 of plants encouraged and the character of their development. It was at 



