32 STUDIES ON PEACHES. 



rate- that the rate of ripening of the green peach is not markedly more 

 rapid than that of the more mature fruit. 



Some problems have arisen in connection with this work, the solu- 

 tion of which must be attended with great difficulty and for which 

 solution a more intimate knowledge must be obtained than is at present 

 possessed of the constituents grouped together under the head of 

 "undetermined." It is probable that an important part of the unde- 

 termined matter consists of pectin bodies, the insoluble pectins of the 

 marc being, with the ripening of the peach or with the storage, con- 

 verted into soluble pectins or other modifications of those bodies. The 

 fact that the juice of the peach does not yield a jelly so readily as is 

 the case with many other fruits would seem to indicate that the soluble 

 pectins are of a different nature from those present in such fruits. The 

 product is doubtless somewhat different from that present in the apple 

 juice. At the same time it is still possible that further modifications 

 of this group may exist in soluble form. There is apparently a tend- 

 ency toward the hydrolization of sucrose with the formation of reduc- 

 ing sugar and the destruction of the reducing sugar in connection with 

 the respiration of the fruit, yielding probably carbon dioxid and 

 water. At the same time the increase of undetermined matter is 

 usually sufficient to account for the decrease of the marc and to explain 

 the latter by the assumption that it may be due to the conversion of 

 insoluble pectin bodies into their soluble modifications. It is probable 

 that the pectins may also be consumed to some extent in connection 

 with the respiration of the peach or may be split up into simpler car- 

 bohydrate bodies. In this investigation it has only been attempted to 

 outline very broadly the changes occurring in the maturity and storage 

 of the peaches. It is hoped that in the near future some worker will 

 find the opportunity to study some of the details whose mastery is essen- 

 tial to the thorough understanding of the problems here discussed. 



