SECTION K.— BOTANY. 



THE GENERAL PHYSIOLOGY OF THE 



PLANT CELL AND ITS IMPORTANCE 



IN PURE AND APPLIED BOTANY 



ADDRESS BY 



PROF. W. STILES, F.R.S. 



PRESIDENT OF THE SECTION. 



Although few subjects are of more importance to the life of man than the 

 physiology of plants, the investigation of this physiology is a field of 

 endeavour which has attracted attention only comparatively recently. 

 A few men, it is true, working in the eighteenth century with the scanty 

 equipment of physics and chemistry then available, did indeed lay the 

 foundations of the science of plant nutrition, but any deep insight into 

 the mode of working of the plant was impossible until, on the one hand, 

 the development of microscopical technique had rendered possible the 

 determination of the internal structure of the organism, and, on the other, 

 the physical and chemical sciences had so far developed as to provide the 

 botanist with information which was fundamental for any sort of under- 

 standing of what took place in the plant. While now the structure of the 

 plant is largely known, the work of the physiologist still waits on the work 

 of the physicist and chemist, and must, of necessity, lag behind develop- 

 ment in physics and chemistry. Occasionally, indeed, the botanist, 

 impatient of this state of affairs, has taken matters into his own hands and 

 has advanced into the field of the physicist and chemist ; perhaps the 

 outstanding example of this is afforded by the work of the botanist 

 Pfeffer in attacking the problems of osmotic pressure, but this is not an 

 isolated case. It is thus no accident that any depth of knowledge of the 

 physiology of plants has been acquired in comparatively recent times. 



The first development in knowledge of the physiology of plants was, 

 as I have already indicated, in the field of plant nutrition. It was made 

 clear during the eighteenth and first half of the nineteenth centuries that 

 the plant absorbed certain substances from its environment and that from 

 these substances the plant body was built up. That the different organs 

 of plants had different functions in this respect also became clear. But 

 up to the middle of the nineteenth century the actual processes taking 

 place in the building up of the plant body from the materials absorbed 

 from the environment were not understood in the least. Nor is this to be 

 wondered at. We know very well now that the complex activities of the 



