80 BOTANY. 



tory process the Starch-making process, or, as it is known 

 in botanidal 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 (O) in the proportion of one atom 

 of the former to two of the latter — (CO,). Water contains 

 Hydrogen (H), two atoms, and Oxygen (0), one atom — 

 (HjO). 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 (Cj^H^oOj,,). 



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 H^^O = 2H -\- O. The free oxygen-atoms 

 are exhaled from the plant, and by the union of carbon 

 oxide and hydrogen the starch is formed: this appears a» 

 minute granules imbedded in the chlorophyll-bodies. 



165. These chemical changes may be shown as follows: 



1200,= ]||C0 .-. starch 



120 H ^^° ®^* ^™^- r = 0„Hao0.o -f 3H»0. 

 12HaO= J24jj' J 



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. 



