PLANT PHYSIOLOGY 119 



must be condensed immediately upon its formation, presumably 

 changing into a simple hexose sugar by addition and rearrange- 

 ment of its molecules, thus n6CH 2 = nC 6 Hi 2 O 6 or glucose from 

 which starch is formed by the loss of water, thus nCeH^Oe 

 nH 2 O = nCeHioO5 or starch. This starch is stored temporarily 

 in the leaves, or it is gathered up as glucose, which is soluble, 

 by the collecting tubes and carried through the vascular bundles 

 to the rhizome where, in the parenchyma cells, it is permanently 

 stored as starch to be used as needed by the plant. At night, 

 in this way the starch is removed from the leaves, but with the 

 advent of daylight the manufacturing process begins again. 

 This process of starch manufacture by photosynthesis is the 

 essential difference between animals and plants, and the plant 

 has this power by virtue of chlorophyll. 



Recent investigations in the chemistry of chlorophyll indi- 

 cate that the reactions taking place in the formation of hexose 

 sugars are far more complex than those outlined in the preced- 

 ing paragraph. Thus pure, extracted chlorophyll, used as a 

 sol with water as the dispersion medium, in a closed vessel con- 

 taining only carbon dioxide, and exposed to light, will not pro- 

 duce formaldehyde. The carbon dioxide and water form car- 

 bonic acid, and this causes the displacement of the chlorophyll 

 magnesium, thus producing yellow phaeophytin (Willstatter) . 

 On the other hand, similarly prepared chlorophyll in a closed 

 vessel containing oxygen and exposed to the light, will lose its 

 color entirely, while formaldehyde is formed in variable quan- 

 tities depending on the length of time of exposure, while the 

 acidity of the system continually increases. This production 

 of formaldehyde may be interpreted as due to oxidation and 

 destruction of the chlorophyll molecule through splitting off and 

 reduction of the alcohol ester (phytol) contained in that mole- 

 cule, while the increasing acidity may be due to the further 

 oxidation of the formaldehyde to formic acid (Jorgensen and 

 Kidd). 



If formaldehyde production in the living plant is a necessary 

 step in the formation of plant sugars, and if it is formed in the 

 manner outlined by Jorgensen and Kidd, then the process of 



