412 Alfred J. Ewart : 



converts the starch into sugar during ripening is not developed ; 

 (2) the cell contains an excess of the product of the diastase 

 reaction, sugar ; (3) the starch grains are composed of some 

 special insoluble form of starch ; or (4) some poison is present in 

 sufficient amount to inhibit the action of the ferment, without 

 necessarily killing the cells until their power of toxic resistance 

 has fallen to a sufficiently low ebb. 



Living pulp cells with undissolved starch grains were soaked 

 in Fehling's solution for half-an-hour, and warmed. Doubtful or 

 no traces of reducing sugar could be detected in them. The 

 same negative result was given after previous warmina* with 

 dilute sulphuric acid. If they contain any sugar at all, they 

 contain less than ordinar}- pulp cells. Further, they do not 

 appear to be either constantly more or less plasmiolysable than 

 ordinary pulp cells. Possibly they contain some substance in 

 solution which makes up for the absence of sugar^. Indeed, if 

 this were not so they would be crushed and flattened during 

 development by the surrounding cells, whereas in adult apples 

 these living starch-bearing cells, though frequently smaller, are 

 often quite as big as the ordinary pulp cells. In any case the 

 non-solution of the starch grains is not due to the cells affected 

 containing an excess of sugar. 



In regard to the diastase ferment the following experiment was 

 performed. Two adult prepared Jonathan apples in which small 

 bitter pits had been produced by 1 per 500,000 and 1 per 

 2,500,000 solutions of lead nitrate, and two ripe normal apples 

 were kept in all for 10 weeks in air at room temperature. Occa- 

 sional cells with uncorroded starch grains were still present in 

 the sound pulp of all four, and in the dead pit tissue of two of 

 them. The peel and dead pit tissue was then removed, and the 

 pounded pulp of each extracted for diastase2. The filtered pre- 

 cipitate from each was divided into two parts, to each of which 

 starch solution was added, and one, the control, was immediately 

 boiled. Both were then kept warm for some hours, and then 

 tested for reducing sugar. 



1 This may lead to a vicious cvcle. Thus the presence of an i?ifinitesinial trace of 

 poison may delay the solution of starch and cause the cell to contain less sugar than its 

 neighbour. It may maintain its osmotic pressure by absorbing salts from them. If these 

 are at all poisonous, the poisoning becomes more severe and may lead to death, some cell* 

 being thus sacrificed as poison traps to preserve the rest. 



2 These tests were performed by Dr. White. 



