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CHAPTER VI. 



Experiments on the Effect of Etherization on Potato-tubers. 



The effect of ether on the nitrogen-compounds of potato-tubers has already 

 been examined by Johannsen who noted with regard to tubers which were yet in 

 the ripening stage that etherization may effect an inverse direction of the meta- 

 bolic processes, the synthesis of proteids being substituted by an increase of the 

 amides [Johannsen 1897, p. 67]. A single experimental-series on the effect of ether 

 on injured potato-tubers seems to show that injury produces an increase of the 

 amides, an effect which the above mentioned author considers to be the normal 

 one; on the contrary etherization seems partly to prevent the increase. The experi- 

 ments on the effect of injury on plants, made by other students, show inverse 

 results. Thus Hettlinger has demonstrated in bulbs a considerable increase of the 

 proteids by injury [Hettlinger 1901]; Marie Leschtsch arrived at the same result 

 [Leschtsch 1903, p. 425], as did Zaleski who concluded that the condensation is 

 produced by the increased supply of oxygen to the tissues; if the injured plants 

 had been exposed to an atmosphere of hydrogen the injury produced no effect, 

 the ratio between the amounts of proteids and of amides remaining constant during 

 the exposure [Zaleski 1901, p. 331]. It remains to be proved whether Zaleski is 

 right in his assumption. Anyhow his proof is not satisfactory, as Palladin [Palladin 

 1888, p. 205, p. 298] and later Godlewski and others have proved that a considerable 

 amount of amino-acids is accumulated in plants which are exempted from the 

 oxygen, the synthesis of proteids being stopped, in all probability because the 

 formation of asparagin has been prevented [Godlewski 1904 p. 141]. Also in split 

 ripening seeds that have been cut across Zaleski found an increase of the con- 

 densation [Zaleski 1905, p. 126]. Kovchoflf, experimenting with bulbs of Allium 

 Cepa, arrived at the same result [Kovchofif 1903, p. 165]. By a single experiment I 

 found that injury will produce too a considerable condensation of the amides of 

 potato-tubers. In order to examine the effect of injury as well as of etherization 

 on potatoes a few experiments were made; however, as the results varied consider- 

 ably, I was induced to make a great many experiments on the subject. 



I have always for the experiments used halved potatoes, the one part was 

 used for the exposure while the other served as a control. When several tubers 

 were used for a single experiment the method was the same, the one portion con- 

 sisting of n halves of n potato-tubers, the other portion being represented by the 

 remaining n halves. The cut was always made lengthwise, perpendicular on the 

 flat side of the tuber, as I considered this division capable of producing the most 

 uniform halves. According to Mûller-Thurgau a most uniform material is to be 

 had by halving the tubers, which he has especially demonstrated with regard to 

 the carbohydrates [Mûller-Thurgau 1882, p. 764]. After the exposure the tubers 



