234 BOTANICAL GAZETTE [march 



The figures of the table show that the actual acidity bears no 

 fixed relation to the total acidity, and that great variations are to 



- 



be found in different plants, as well as in different tissues of the 



same plant. 



The figures for actual acidity are surprisingly high in the case 



of the lemon and of the cranberry, especially in view of the 

 prevalent opinion that protoplasm demands a neutral or nearly 

 neutral reaction for normal metabolism. It is of interest, there- 

 fore, to inquire whether the figures represent the actual acidity of 

 the protoplasm. In the lemon the acid juice is contained in sacs, 

 the walls of which are composed of living cells, while the cavity is 

 produced by the disintegration of cells. Reed 8 has shown that 

 the living cells of the walls contain oxidases whose activity is 

 promptly inhibited by the acid contained in the cavity of the sac. 

 Since the oxidases are active in the living cells, it follows that the 

 protoplasm is by no means as acid as the juice in the sacs, and 

 hence the figures given in table I cannot apply to the protoplasm 

 in the case of the lemon. 



With the cranberry the case seems to be different. In this 

 fruit there are no sacs such as are found in the lemon; the juice is 

 contained entirely in the cells. It is important, therefore, to 

 ascertain whether these cells are dead or alive. In order to test 

 this, the outer colored layer of cells was removed and the following 

 results were obtained on the colorless cells: 



Eosin failed to penetrate unboiled peeled cranberries, but 

 penetrated readily into the boiled peeled cranberries. The diffi- 

 culty due to the precipitation of eosin in acid solutions was obvi- 

 ated by frequent renewal of the eosin solution. 



2. Ripe cranberries can be peeled without staining the white 

 tissue beneath, while this is not possible in overripe, soft 

 cranberries. 



3. Unboiled, peeled cranberries in a red watery extract of cran- 

 berry peeling were unstained after several hours, while the indicator 

 readily penetrated the boiled peeled cranberries. 



All these tests go to show that the living cells of the cranberry 

 have an actual acidity which is extremely high. It is quite pos- 



8 Reed, G. B., Box. Gaz. 57:528. 1914. 



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