164 HOW CROPS GROW. 
sential, and what are really accidental ingredients, or what 
amount of any given ingredient is essential, and to what 
extent it is accidental. Wolff, who appears to have first 
suggested that a part of the ash of plants may be acci- 
dental, endeavored to approach a solution of this question, 
by comparing together the ashes of samples of the same 
plant, cultivated under the same circumstances in all re- 
spects, save that they were supplied with unequal quantities 
of readily available ash-ingredients: The analyses of the 
ashes of buckwheat-stems, just quoted, belong to this in- 
vestigation. Wolff showed that, by assuming the presence 
in each specimen of buckwheat-straw of a certain excess 
of certain ingredients, and deducting the same from the 
total ash, the residuary ingredients closely approximated 
in their proportions to those observed in the crop which 
grew in-an unmanured soil. The analyses just quoted, 
(p. 163,) are here “ corrected” in this manner, by the sub- 
traction of a certain per cent of those ingredients which 
in each case were furnished to the plant by the fertilizer 
applied to it. The numbers of’ the analyses correspond 
with those on the previous page. 
1 2 3 4 5 6 
20 p. ¢. bat a 8.5p.¢c 16.67. ¢. 
oh bride Carbonate a onate Sulphate Carbonates 
A, ar deduction of of of Of li lime und 
oisaiauatmarean ae at i Boneh gnesit 9 
Potash: sipevaaigtaaancsian 3 r 30.6 28.0 
Chloride of potassium. = 7 : 1 ah 3.9 4 11.8 
Chloride of sodium.... 4.6 3.8 4.0 4.7% 3.7 1.9 
DADA Cys accesie cider cie tiecate 15.7 17.3 16.0 14.5 15.3 14.6 
Magnesia............65 Lt 2.4 4.1 1.7 2.3 2.9 
Sulphuric acid.... .... 4.7% 3.5 3.4 5.4 pee 4.1 
Phosphoric acid....... 10.3 11.7 8.1 11.2 11.8 11.7 
Carbonic acid......... 20.4 20.1 25.9 19.8 21.6 19.3 
BUNCE, cies ecrereacne Sel otace 3.6 5.2 5.2 5.3 5.2 6.1 
100.0 100.0 100.0 100.0 100 0 100.0 
The correspondence in the above analyses thus “cor- 
rected,” already tolerably close, might, as Wolff remarks, 
(loc. cit.) be made much more exact by a further correc- 
tion, in which the quantities of the two most variable in- 
