68 ON THE ORIGIN AND ACTION OF HUMUS. 



now produce sugar, amylin or starch, and acids, 

 which were previously formed by the roots, when 

 they were necessary for the development of the stem, 

 buds, leaves, and branches of the plant. 



The organs of assimilation, at this period of their 

 life, receive more nourishment from the atmosphere 

 than they employ in their own sustenance; and when 

 the formation of the woody substance has advanced 

 to a certain extent, the expenditure of the nutriment, 

 the supply of which still remains the same, takes a 

 new direction, and blossoms are produced. The 

 functions of the leaves of most plants cease upon 

 the ripening of their fruit, because the products of 

 their action are no longer needed. They now yield 

 to the chemical influence of the oxygen of the air, 

 generally suffer a change in color, and fall off. 



A peculiar " transformation " of the matters con- 

 tained in all plants takes place in the period between 

 blossoming and the ripening of the fruit; new com- 

 pounds are produced, which furnish constituents of 

 the blossoms, fruit, and seed. An organic chemical 

 "transformation" is the separation of the elements 

 of one or several combinations, and their reunion 

 into two or several others, which contain the same 

 number of elements, either grouped in another man- 

 ner, or in different proportions. Of two compounds 

 formed in consequence of such a change, one remains 

 as a component part of the blossom or fruit, while 

 the other is separated by the roots in the form of 

 excrementitious matter. No process of nutrition 

 can be conceived to subsist in animals or vegetables, 

 without a separation of effete matters. We know, 

 indeed, that an organized body cannot generate 

 substances, but can only change the mode of their 

 combination, and that its sustenance and reproduc- 

 tion depend upon the chemical transformation of the 

 matters which are employed as its nutriment, and 

 which contain its own constituent elements. 



Whatever we regard as the cause of these trans- 

 formations, whether the Vital Principle, Increase of 



