NATURE OF PLANTS 13 



not known. It has been suggested that CO2 and HoO enter into 

 solution forming carbonic acid (H2CO3). This change is repre- 

 sented by the equation, CO2 + HoO = H2CO3. By giving off 

 one part of oxygen this acid is changed to formic acid (CH2O2), 

 i. e., H2CO3 = CH2O2 + 0. A similar decomposition is effected 

 in the formic acid which results in the formation of formalde- 

 hyde (CH2O), i. e., CH2O2 = CH2O + 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 CH2O would give C6H12O6 or grape sugar. This is but a 

 theory based upon the facts that CO2 and H2O do unite in nature 

 to form H2CO3 and that this acid may decompose as stated 

 above, and finally that formaldehyde can be detected in plant 

 hairs 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 for- 

 mation of the carbohydrates relates solely to the beginning and 

 end of the process. Water and carbon-dioxide enter the chlor- 

 enchyma cells. A series of changes follows, the nature of which 

 can only be conjectured. Finally, as the end result, sugar ap- 

 pears 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 

 CO2 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 



