368 H. A. SPOEHR 



In these reactions the inorganic salts play the role of enzymes, 

 and in all probability enzymes act by virtue of their ability to 

 form salts with sugars. Even in these relatively crude experi- 

 ments great differences in the reactions of the various sugars 

 appear; it is therefore not surprising that the far more delicately 

 adjusted enzymatic reactions should exhibit large variations in 

 the reactivity of the various hexose and pentose sugars. 



That the pentoses are of great physiological importance to 

 the plant becomes evident in the light of recent investigations 

 on the chemistry of the cell nucleus.^ Among the chief compo- 

 nents hereof are the so-called nucleic acids. These are highly com- 

 plex substances consisting roughly of a combination of phos- 

 phoric acid, purines, pyrimidines and several carbohydrate 

 groups. While in the nucleic acids of animal origin the carbo- 

 hydrate is a hexose, the plant nucleic acids so far studied have 

 been found to contain the pentose group. The function and 

 fundamental importance of the nucleus in the metabolism of the 

 plant need no further discussion here; however, a more intimate 

 knowledge of the chemical composition and action will undoubt- 

 edly lead to a clearer understanding of the intricate reactions of 

 this most important organ. 



As a further illustration of the role of pentoses in the more in- 

 tricate metabolism of certain plants the relation of these sugars 

 to rubber and terpene formation is of special interest. Harries* 

 in his extensive investigations on the constitution of para- 

 caoutchouc has shown that this substance is made up of a large 

 number of groups which have been condensed or polymerized to 

 form an exceedingly large molecule. These individual groups 

 have the composition, CsHg, and thus rubber can be considered 

 as being composed of a number of these groups in a similar man- 

 ner as we think of starch and cellulose as a multi-anhydride of 

 glucose. As the sugars are the first products of the primary or- 

 ganic synthesis in the plant practically all other organic sub- 

 stances found therein must be derived from them more or less 

 directly. Harries considers the CsHs groups as reduction prod- 



* Levene, J. and W. Jacobs, Ber. d. deutsch. chem. ges. 43: 3147, 3164, 1910. 



* Harries, C, Ber. d. deutsch. chem. Ges. 38: 1195-1203, 1905. 



