80 BOTANY. 
“tory process the Starch-making process, or, as it is known 
in botanical books, Assimilation. 
153. We cannot yet give an exact account of the suc- 
cessive steps in the manufacture of starch. The principal 
facts, however, are as follows: Carbon dioxide contains 
Carbon (C) and Oxygen (QO) in the proportion of one atom 
of the former to two of the latter—(CO,). Water contains 
Hydrogen (H), two atoms, and Oxygen (O), one atom— 
(H,O). Both water and carbon dioxide are decomposed in 
the chlorophyll-granules of leaves and other green parts of 
plants. After decomposition there is such a recombination 
as to produce Starch (C,,H,,0,,). 
154. The carbon dioxide is probably decomposed into 
carbon oxide (CO) and free oxygen (O): thus CO,=CO + O. 
At the same time water is decomposed into hydrogen and 
oxygen: thus HO=2H-+0. The free oxygen-atoms 
are exhaled from the plant, and by the union of carbon 
oxide and hydrogen the starch is formed: this appears as 
minute granules imbedded in the chlorophyll-bodies. 
155. These chemical changes may be shown as follows: 
1200, = { 12CO ccisctetacrniedic starch 
AG ; = 240 set free. } = CiaHa0Oi0 + 2H,0. 
WHO = | OAT ccc, 
Here twelve molecules of carbon dioxide and twelve mole- 
cules of water produce one molecule of starch and two 
molecules of water (water of organization), while twenty- 
four atoms of oxygen are set free and permitted to escape 
from the cells into the surrounding air or water. 
In some plants no starch is formed in the chlorophyll, 
but oily or sugary matters which have nearly the same 
chemical significance. 
