160 HOW CROPS GROW. 
Wheat. Rye. Maize. Skénless Skinless 
Average Average Average oats. barley. 
of of Analysis Analysis 
seventy-nine twenty-one seven by Fr. by Fr. 
analyses. analyses. analyses. Schulze. Schulze. 
Peteah:.. ..0..... 31.3 28.8 27.7 33.4 85.9 
GHB Sees sticels oe2 3.2 4.3 4.0 oa 1.0 
Magnesia........ 12.3 11.6 15.0 11.8 pea 
PUNIG. 2. cctak ce se 3.2 3.9 1.9 3.6 2.9 
Oxide of Iron... 0.7 0.8 1.0 0.8 0.7 
Phosphoric acid.46.1 45.6 47.1 46.9 15.0 
Sulphuric acid... 1.2 1.9 ierg —_— = 
Bien cctiacas<s 1.9 2.6 2.1 2.4 0.7 
Chlorine....... 0.2 0.7 0.1° —. —. 
that the pea and bean kernel, together with the allied vetch 
and lentil, (p. 379, )also nearly agree in ash-composition. 
So, too, the ashes of the root-crops, turnips, carrots, and 
beets, exhibit a general similarity of composition, as may 
be seen in the table, (p. 154-5). 
The seeds of the oil-bearing plants likewise constitute a 
group whose members agree in this respect, p. 379. 
5. The ash of the same species of plant is more or less 
variable in composition, according to circumstances, 
The conditions that have already been noticed as in- 
fluencing the proportion of ash are in general the same 
that affect its quality. Of these we may specially notice: 
a. The stage of growth of the plant. 
b. The vigor of its development. 
c. The variety of the plant or the relative development 
of its parts, and 
d. The soil or the supplies of food. 
a. The stage of growth. The facts that the different 
parts of a plant yield ashes of different composition, and 
that the different stages of growth are marked by the 
development of new organs or the unequal expansion of 
those already formed, are sufficient to sustain the point 
now in question, and render it needless to cite analytical 
evidence. In a subsequent chapter, wherein we shall at- 
tempt to trace some of the various steps in the progressive 
