410 Alfred J. Ewart : 



absorption of minute traces of poisons through the roots, or less 

 probably, of volatile substances from the air. 



To determine this, young apples three weeks old, as yet with 

 no starch, were finely punctured just through the skin, and 

 rubbed over with arsenate of lead. At three months all those 

 remaining on the tree showed deep brown spots at or below 

 the point of injury, and in some cases it was difficult to trace 

 any connection with the injury on the skin. The dead tissue in 

 this case contained few starch grains as compared with the 

 normal pulp, but this was because most of the cells were killed 

 before the deposition of starch grains had begun in the pulp 

 tissue. 



The stapch grains of bitter pit. 



One of the characteristic features of bitter pit is stated to 

 be that cells filled with starch grains occur in the dead tissue 

 when none are present in the healthy pulp cells. Out of some 

 hundreds of artificial bitter pits examined which had been 

 produced by different poisons, practically in every case where 

 the pits were sufficiently large, occasional isolated cells packed 

 with starch grains could be detected. At first this appeared to 

 point to a condensation of starch in the cells as they were 

 gradually killed by minute traces of poison. Prepared adult 

 apples floated on dilute non-poisonous solutions of glycerine, 

 sugar and formaldehyde, showed no perceptible formation and 

 accumulation of starch in the pulp cells under the prepared 

 spots, so that apparently the leucoplastids in adult pulp cells, 

 which still appear to be present in some cases particularly near 

 the surface, appear to have lost the power of producinc: starch. 

 Further investigation showed that the presence of occasional 

 cells, or even groups of cells living but packed with starch 

 grains, is a common and almost universal occurrence in ripe 

 apples. The sound pulp of more than 200 ripe apples of the 

 kinds mentioned above was examined for starch, and in 95 per 

 cent, with positive results. These starch cells are always 

 sparsely scattered in sound apples, and are least abundant in 

 Five Crowns and most in Jonathans. The individual starch cells 

 when present are, however, packed with starch grains showing 



