24 A Neiv Point of Resemblance in the 



a similar surface, and a little of a strong solution of iodide 

 of potassium added, the starchy particles will become gra- 

 dually brown and then black from the formation of iodide 

 of starch. Here^ then, we have the recognised reactions 

 characteristic of the presence of ozone. The rapidity and 

 intensity of these reactions will be found to vary with 

 different articles or different specimens of the same article ; 

 and they may fail altogether, as in very watery fruits, such as 

 some grapes, though even with these the guaiac reaction 

 may be perceptible in a green berry from the same bunch. 

 I have not observed this reaction with the soft pulpy 

 fruits which quickly decay, such as the strawberry or peach, 

 perhaps because the specimens were not fresh enough, 

 while with the apple and pear both reactions may be 

 obtained though the fruits have been pulled for a consider- 

 able time. 



With reference to the agent providing these reactions it 

 may certainly be said: — (1.) That it is not merely ordinary 

 oxygen absorbed and dissolved in the vegetable juice ; and 

 this, both on account of these reactions and from the fact 

 that Cahours (Comptes Rendus, 1864, LVIIL, pp. 495 and 

 653) could obtain carbonic acid gas and nitrogen, but never 

 oxygen, from expressed fruit juices. (2.) It is not newly- 

 formed oxygen, separated by the chlorophyll, which may 

 possibly in part be diffused into the structures below the 

 surface as well as liberated into the atmosphere, since 

 Pellucci has shown (Chemisclies Centralhlatt, 1872, p. 356) 

 that the oxygen developed under water in sunlight by various 

 plants does not act on starch and iodide of potassium like 

 ozone, agreeing therein with the results obtained by Mulder 

 and others, v. Hoppe-Seyler's Physiologische Chemie, 1877, 

 p. 47. These reactions are also given by sections of pulled 

 fruits, which, though capable of carrying on a process of 

 respiration for a time, no longer liberate oxygen ; and also 

 by underground organs like the potato, turnip, &c., which 

 never perform that function. (3.) It is not probable, in 

 spite of these reactions, that the substance is actually dis- 

 solved ozone, since it is scarcely conceivable that it could 

 continue to co-exist for any length of time with the complex 

 mixture of solid and dissolved organic matters contained in 

 fruits. We are therefore in a manner shut up to the con- 

 clusion — (4.) That the oxygen is in a form of loose com- 

 bination, as it is in the blood, and therefore capable of being 

 slowly given off in a very active form to combine definitely 



