THE ASH OF PLANTS. 179 



In the first place, however, we are not warranted 

 in assuming that the "excess" of potassium chloride, 

 potassium carbonate, etc., deducted in the above analyses 

 respectively, was all accidental and unnecessary to the 

 plant, for, under the influence of an increased amount of 

 a nutritive ingredient, the plant may not only mechani- 

 cally contain more, but may chemically employ more in 

 the vegetative processes. It is well proved that vegeta- 

 tion, grown under the influence of large supplies of nitro- 

 genous manures, contains an increased proportion of 

 truly assimilated nitrogen as albuminoids, amido-acids, 

 etc. The same may be equally true of the various ash- 

 ingredients. 



Again, in the second place, we cannot say that in any 

 instance the minimum quantity of any ingredient neces- 

 sary to the vegetative acts is present, and no more. 



It must be remarked that these great variations are 

 only seen when we compare together plants produced on 

 poor soils, i. e., on those which are relatively deficient in 

 some one or several ingredients. If a fertile soil had 

 been employed to support the buckwheat plants in these 

 trials, we should doubtless have had a very different 

 result. 



In 1859, Metzdorf (Wilda's CentralUatt, 1862, II, p. 

 367) analysed the ashes of eight samples of the red- 

 onion potato, grown on the same field in Silesia, but dif- 

 ferently manured. 



Without copying the analyses, we may state some of 

 the most striking results. The extreme range of varia- 

 tion in potash was 5 per cent. The ash containing the 

 highest percentage of potash was not, however, obtained 

 from potatoes that had been manured with 50 pounds of 

 this substance, but from a parcel to which had been ap- 

 plied a poudrette containing less than three pounds of 

 potash for the quantity used. 



The unmanured potatoes were relatively the richest in 



