330 



Sir J. B. Lawes and Sir J. H. Gilbert. 



It was found that the chemical composition of the mixed herbage 

 was very directly dependent, not only on the seasons and on the sup- 

 plies within the soil, but very prominently also on the description of 

 plants encouraged, and on the character of their development ; so 

 that it was essential to a proper interpretation of the variations in the 

 chemical composition, to bear in mind the differences in the botanical 

 composition. Hence a summary table was given showing the character- 

 istic differences in the botanical composition under the different con- 

 ditions as to manuring, the influence of which on the chemical com- 

 position it was sought to illustrate. 



As the investigation involved the consideration of the chemical 

 composition of the mixed produce of about twenty plots over forty or 

 more seasons, including the discussion of the results of more than 200 

 complete analyses of the ashes of the separated or the mixed herbage, 

 attention was called to the state of existing knowledge as to the role or 

 function in vegetation of the individual constituents found in the 

 ashes of plants ; and this was seen to be very imperfect. Further, 

 in calculating the percentage composition of the " pure ash," the plan 

 usually adopted was to exclude not only the sand and charcoal, but 

 also the carbonic acid. The authors considered, however, that the 

 presence and the amount of carbonic acid associated with the fixed 

 constituents in plant-ashes was a point of considerable significance ; 

 and they entered into some detail as to the methods of determining 

 the carbonic acid in ashes, and as to the results obtained. 



In order to throw some light on the connection between the growth 

 of the crops and their mineral composition, results relating to the 

 separated gramineous, the separated leguminous, and the separated 

 " miscellaneous " herbage of the mixed produce, grown without manure 

 and by different manures, were first discussed. To obtain more 

 definite evidence illustrating the connection between character and 

 stage of growth and the composition of the products — especially the 

 ash-composition — results relating to the bean plant, taken at succes- 

 sive periods of growth, and also to the first, second, and third crops of 

 clover, were next considered. Lastly, in further illustration, results 

 as to the nitrogen and the ash-composition of crops of three different 

 natural orders— wheat representing the Graminese, Swedish turnips the 

 Cruciferse, and beans and clover the Leguminosese — were given. 



The general result was, that there were very characteristic differ- 

 ences in the composition of the ashes of different crops according to 

 the amounts of nitrogen they assimilated. Red clover, for example, 

 yields large amounts of nitrogen over a given area, part of which is 

 due to fixation, but much is certainly taken up as nitrates from the 

 soil ; and the results show, that the greater the amount of nitrogen 

 assimilated the more is the ash characterised by containing fixed base 

 in combination with carbonic acid ; presumably representing organic 



