PHYSIOLOGY OF NUTRITION 99 



story to you in a more connected form. Meanwhile let 

 us enquire what the physiologists had been doing and 

 how far they had made progress since Ingen-Housz and 

 De Saussure had opened up new vistas in the subject, 

 and set out new problems for solution. You will most 

 readily gain an insight into the condition of plant 

 physiology at or about the year 1830 by studying De 

 Candolle's account as it appeared in his Physiologic 

 vegetate, published in 1832, and which I will quote to 

 you in full. Here is his view of plant nutrition : 



'' The spongioles of the root " (in reality the growing 

 apices) " being actively contractile and aided by the 

 capillarity and hygroscopic qualities of their tissue, 

 suck in the water that surrounds them, together with 

 the saline, organic, or gaseous substances with which it is 

 laden. By the operation of an activity which is mani- 

 fested principally in the contractility of the cells and 

 perhaps also of the vessels, and is maintained by the 

 hygroscopic character and capillarity of the tissue of the 

 plant and also by the interspaces produced by expiration 

 of the air and by other causes, the water sucked in by 

 the roots is conducted through the wood, and especially 

 in the intercellular spaces, to the leaf-like parts, being 

 attracted in a vertical direction by the leaves and in a 

 lateral direction by the cellular envelope at every period 

 of the year, but chiefly in the spring ; a considerable part 

 of it is exhaled all day long through the stomata into the 

 outer air in the form of pure water, leaving in the organs 

 in which the evaporation takes place all the saline, and 

 especially all the mineral, particles which it contained. 

 The crude sap which reaches the leaf-like parts of the 

 plant there encounters the sunlight, and by it the carbonic 

 acid gas held in solution by the sap, whether derived 

 from the water sucked in by the roots or from the 

 atmospheric air, or being part of that which the oxygen 

 of the air produced with the surplus carbon of the plant, 

 is decomposed in the day time ; the carbon is fixed 



