NATURE OF PLANTS 13 



It has been suggested that CO 2 and H 2 O enter into solution form- 

 ing carbonic acid (H 2 CO 3 ). This change is represented by the 

 equation, CO 2 + H 2 O = H 2 CO 3 . By giving off one part of 

 oxygen this acid is changed to formic acid (CH 2 O 2 ), i. e., H 2 CO 3 

 CH 2 O 2 + O. A similar decomposition is effected in the formic 

 acid which results in the formation of formaldehyde (CH 2 O), 

 i. e.j CH 2 O 2 = CH 2 O + O. The two parts of oxygen pass 

 from the cells and escape through the stomata as a gas. In 

 the presence of certain alkalies and acids, formaldehyde increases 

 the number of elements which compose it, thus six times CH 2 O 

 would give C 6 HioO c or grape sugar. This is but a theory based 

 upon the facts that CO 2 and H 2 O do unite in nature to form 

 H 2 CO 3 and that this acid may decompose as stated above, and 

 finally that formaldehyde can be detected in plant cells and it 

 is possible to produce sugar from this substance by treating it 

 with alkalies and acids. All that can be definitely stated about 

 the changes going on in the leaf, during the formation of the 

 carbohydrates relates solely to the beginning and end of the 

 process. Water and carbon dioxide enter the chlorenchyma 

 cells. A series of changes follows, the nature of which can only 

 be conjectured. Finally, as the end result, sugar appears in 

 the cells and oxygen is set free, escaping as a gas. 



These complex changes are brought about in the leaf in so 

 subtle a way that we are not conscious of them or of the great 

 amount of energy that is required to effect them. It requires 

 the energy expressed by a temperature of 1300 C. to decompose 

 CO 2 into its elements. Where does the plant obtain the energy 

 to bring about the decompositions and recomposition? This 

 work is accomplished by the energy of the sunlight acting upon 

 the chloroplasts. The chloroplasts of the seed plants are minute, 

 rather lens-shaped grains, and increase in number by the division 

 of the plastid into two equal parts (Fig. 9). These bodies are 

 denser portions of the cytoplasm and like it are nearly colorless. 

 In the presence of light a green, oily substance, chlorophyll, is 

 formed in the plastids, thus producing their green color. Chloro- 

 phyll is rarely formed except in the presence of light. Plants 

 grown in cellars or in the dark are of a pale color owing to the 



