38 ASSIMILATION OF HYDROGEN. 



30 eq. carbonic acid and 24 eq. hydrogen derived ) _/vj ofTurvtntxnt 



from 24 eq. water > 



with the separation of 84. eq. oxygen. 



It will readily be perceived that the formation of the acids is 

 accompanied with the smallest separation of oxygen ; that the 

 amount of oxygen set free increases with the production of the 

 so-named neutral substances, and reaches its maximum in the 

 formation of the oils. Fruits remain acid in cold summers ; 

 while the most numerous trees under the tropics are those which 

 produce oils, caoutchouc, and other substances containing very 

 little oxygen. The action of sunshine and influence of heat 

 upon the ripening of fruit is thus, in a certain measure, repre- 

 sented by the numbers above cited. 



The green resinous principle of the leaf diminishes in quan- 

 tity, while oxygen is absorbed, when fruits are ripened in the, 

 dark ; red and yellow coloring matters are formed ; tartaric, 

 citric, and tannic acids disappear, and are replaced by sugar, 

 amylin, or gum. 6 eq. Tartaric acid, by absorbing 6 eq. oxygen 

 from the air, form grape sugar, with the separation of 12 eq. 

 carbonic acid, 1 eq. Tannic Acid, by absorbing 8 eq. oxygen 

 from the air, and 4 eq. water, form 1 eq. of Amylin, or starch, 

 with separation of 6 eq. carbonic acid. 



We can explain, in a similar manner, the formation of all the 

 unazotized component substances of plants, whether they are 

 produced from carbonic acid and water, with the separation of 

 oxygen, or by the conversion of one substance into the other, 

 by the assimilation of oxygen and separation of carbonic acid. 

 We do rot know in what form the production of these constitu- 

 ents takes place ; in this respect, the representation of their 

 fDrmation which we have given must not be received in an 

 absolute sense, it being intended only to render the nature of 

 the process more capable of apprehension ; but i> must not be 

 forgotten, that if the conversion of tartaric acid into sugar, in 

 grapes, be considered as a fact, it must take place under <ill cir- 

 cumstances in the proportions al»ove mentioned. 



The vital process in plants is, v ith reference to the point we 

 have been considering, the converse of the chemical processes 

 engaged in the formation of salts. Carbonic acid, zinc, and 



