Significance of Functional Metabolism in the Plant. 93 



CROONIAN LECTURE. " The Nature and Significance of Func- 

 tional Metabolism in the Plant" (Das Wesen und die, 

 Bedeutung des Betriebsstofwechsels in der Pflanze). By 

 WILHELM PFEFFER, Sc.D. (Cantab.), of the University of 

 Leipzig, For. Mem. R.S. Received March 9, Read March 

 17, 1898. 



(Translation of Author's Abstract.) 



The fact that a mould fungus will thrive in a solution, from 

 which, with the exception of certain inorganic acids, it can obtain 

 nothing but sugar, affords proof that the elaboration of these food 

 substances in metabolism not only provides the numerous carbon com- 

 pounds which are concerned in the construction of the plant, but also 

 serves as a sufficient source of energy for the performance of its func- 

 tions. For in the plant, as in the animal, vital activity comes to 

 a standstill if the conditions and the energy necessary for the discharge 

 of its functions are not constantly provided by means of profound 

 chemical decompositions. Just as in animals, a great amount of 

 internal and external work has to be accomplished, in order to carry 

 on and maintain the action of the organism. Hence the greater 

 part, and in the mature plant even the whole, of the food absorbed 

 is devoted to this functional metabolism, so that only a certain 

 fraction of the sugar which has disappeared from the solution is 

 to be found in the resulting crop of fungi, in the form of various 

 carbon compounds. The rest of the sugar has been burnt up to form 

 carbonic acid and water ; that is to say, it has been sacrificed to the 

 physiological combustion, which in these, as in most plants, is 

 indispensable for gaining an adequate amount of kinetic energy. 



But, just as man is able to obtain driving power, not only from the 

 combustion of wood and coal, but also from the explosion of gunpowder 

 or dynamite, so there are certain of the lower plants which gain 

 their whole kinetic energy by means of chemical transformations and 

 decompositions, which go on without the participation of free 

 oxygen. Although the careful consideration of such organisms is 

 indispensable for any correct estimate of functional metabolism, yet 

 we may, in the first instance, limit our attention to oxygen-respira- 

 tion, i.e., to the functional metabolism of aerobic organisms. 



In any case it is only after elaboration that food acquires its 

 significance for the construction and working of the organism. 

 With respect to the utilisation of the food, it is of no consequence 

 whence it comes, or by what means the organism obtains it. 

 Obvious as this consideration is, yet confusion between the elabora- 

 tion of food in structural and functional metabolism on the one 



