44 Alfred J. Ewart: Bitter Fit in Apples. 



living. The vac\iolar meinbraiR-e is iinpernieable to the ari«ls of the 

 cell sap. When a metallic poison whicli (le.stioys oxidase is applied 

 -externally, alkali and oxygen may Lome into contact with the tannic 

 acid and produce browning, before the vacnolar inenil)iane becomes 

 permeable to the acid of the cell sap. When the cells are killed by 

 boiling oxidase is destroyed, and the vacuolar membrane allows 

 acid to escape immediately, and neutralise the alkalinity of the 

 protoplasm, so that tlie piill> ren)ains colonrless until alkali is 

 added. When the cells are phued in toxic but very dilute sul- 

 phuric acid, browning occurs before the alkalinity of tlie protoplasm 

 is removed, or before the oxidase is destroyed. With stronger acid 

 solutions the oxidase is destroyed or the alkalinity is removed before 

 the tannic acid has time to oxidise, and no browning takes place. The 

 brown oxidation products rapidly unite with the proteids of the cell, 

 and the colour is then very permanent. Carbon dioxide and unaltered 

 cell sap are non-poisonous to the pulp cells. Tannic acid is less 

 poisonous than any other acid tried, and alcohol is less poisonous 

 than lime water. 



Yates' apples do not appear to be capable of more than a month's 

 strict anaerobiosis in hydrogen or carbon dioxide at room tempera- 

 ture. In a cool chamber the period Avouhl piobal)ly l)e prolonged. 

 Apples can he preserved to a remarkable extent by loatiTig them 

 "with a gelatine skin. Peeled apples will remain living foi- a fort- 

 night longer under kerosene, and the fungus Pencillium will grow 

 upon them and upon potato slices submerged in kerosene. 



DESCRIPTION OF PLATES. 



Plate III.— Localised ).oisoning, with 1 per 1 .000. 000. Odd of mer- 

 curic chloride. 



i\ . — Fig. 1 . Portion of vascidar system of ap]>le x 12^. 

 Fig. "2 . Poition of vascular system of apph' x 29. 

 \'"\\l. -5 . Endings of vascular bundles in apple pnlj) x 22. 



V. — Fig. 1 . A))ples i)eeled on one side and ])lackene<l witji 



ferric cliloride. 

 Kig. 2 . Poi-tions of blackened pulp cells x lo. showinu' 



tannic acid vacuoles. 

 Fig. ;5 . Tannic Atid vacuoles in protoplasm of pulp 



cells stained with ferric rlilori.le x ;{20. 

 Fig. 4. Do., stained with methyl blue x 400. 



