Bitter Pit and Sensitivity to Poisons. 2;i9 



to a plant tissue withtnit exercising any additional injuiious in- 

 tlueiu'e. 



Any staiH-li gfains. however, \vhieli wei'e extruded into the cell- 

 sap would l)e protected from diastatic action, and hence it Avas of 

 interest to deterniine thi'ii- actual position \n l)itter pit cells, and 

 in those occasional starch-beai-ing cells, which so frequently occur 

 in healtliy ptdp tissue. Sections of hitter pit and healthy pulp 

 were stained with iodine, and examined in a horizontal micro- 

 scope. -After notinu' the position of the starch grains, the stage- 

 was rotated through ISO^. It is easy to see in tliis way that cer- 

 tainly 99 per cent, of the starch is in tlie protoplasm. Very 

 occasionally a large starch grain can be seen to be lying in the 

 vacuole, and to move when the cells are turned upside down. The 

 same is shown in carefully teased preparations. In the l)rown 

 starch l)earing tissue formed by bruising an apple when it is in 

 the starch stage of development, free starch grains lying in the 

 vacuole are much commoner, l)ut even here by far the greater 

 number of the starch grains always remain in the dead proto- 

 plasm. Any starch grains lying in the vacuole after j^i'olonged 

 contact with tannic acid would become more resistant to diastatic 

 action. Probably this is the explanation of the occurrence of occa- 

 sional resistant grains in the .starch of both normal and bitter pit 

 pulji. The fact that treatment with dilute hydrochloric acid makes 

 these grains more readily dissolved by diastase is not neces- 

 sarily due. as I formerly supposed to be the case, to the removal of 

 a poison inhibiting ferment action, but is possibly due to the 

 acid removing the peculiar insoluble or difficultly soluble condition 

 into which contact with tannic acid throws starch. 



T/ie Dldxfdsc Metliod of Deffcfitiri Poisons. 



That this method of detecting extraneous poisons in bitter pir 

 tissue would be a failure might have been predicted from the 

 foregoing facts. Indeed, since metallic poisons usually combine 

 with the proteids of the cell, a cell width had just i-eceived enough 

 to poison it might have little or no available suiplus to poison a 

 second cell or a solution of diastase. 



Cubes of apple pulp weighing 5 grams were floated for two 

 days on (a) Avater, (b) 1 per 1,000,000 mercuric chloride: (a) 

 browned on the surface, (b) more deeply, and a duller brown. Each 

 was then pounded up, 10 c.c. of 0.05 per cent, diastase added 

 and filtered after each day. 5 c.c. of each filtrate were added to 



