;30 Alfred J. Ewart : 



<hie to the soil containing more imnius. which has a iXDiiouneeil 

 retentive and restraining action upon many mineral poisons, as 

 compared with sandy soils. 



77/ e browning of the puly cells. 



According to McAlpine (Report p. 12), the l)rowninL^ of dead 

 pulp tissue is due to a change in the cell walls, and " tlie- guirnny 

 or mucilaginous substance which colours them brown is of a pectic 

 •character." As a matter of fact tlie Ijrown colour is not in the 

 cell wall, but in the protoplasm within it; it is not of a pectic 

 character, and it is not either gummy or mucilaginous. 



Lindret (Le Cidre, p. 150, 1893) conchnled that an oxidase fer- 

 ment was present which carries oxygen to the tannin of the cell 

 iind causes a production of dark coloured oxy-compouiids whioh 

 are precipitated upon the cell walls as a permanent dye. Behrens 

 <Centralbl. f. Bakt. 2 abt. 1898, Bd. 4. S. 5U) explained the brown 

 colour as being due to the combination of a direct oxidation pro- 

 duct of the tannic acid of the fruit, with the proteids of the cell. 

 Before any definite conclusions can be made, however, it is neces- 

 sary to know the distribution of the tannic acid in the cell. 

 Avhether an oxidase ferment is pi-esent or necessary, wliethei' a 

 brown colouration can be produced in tlie absence of free oxygen, 

 and what are the influences of different external conditions on the 

 browning. 



T/ie (listrihutioii of fhe faiinin in ihe. cell. 



Sap rapidly expressed by strong pi-essure from Statesman. Sturmer 

 Pippin and Yates' apples, and filtered i-apidly with the aid (vf a 

 suction pump in 1-.3 minutes, is quite colourless, and remains so on 

 standing. It contains an iron-greening form of tannic arid. 



The pressed pulp rapidly browns in air. and witli l'"c<'l;j tiii-iis 

 black. Hence one at least of the sul)stances causing browning is not 

 in the cell sap, but in the protoplasm or cell walls of the pulp cells. 

 The black colour with Fe ('1., is produced rapidly with crushed cells, 

 and is darker than ])efore the sa]) was pressed out, but with living 

 cells it only ap])(>ars.as the Vv ('!., penetrates the piotoplasm anil 

 kills it. In freshly browned j-ulp. the colour is not in the cell wall, 

 but in tlie i.rotoplasm. 



The residue of ])ulp cells on the filter in all cases slowly turns 

 deep brown in air and turns daik with i'\' ("1 ;. .Vt tir.st it may con- 

 tain .still living ptdp cells, and Ihmicc gives the Fe Cl^ reaction 

 more rapidly on boiling. Sap tillered from pressed jndp after 



