104 PLANT PHYSIOLOGY 



sciences. It is often to be blamed for a classification of the sciences 

 in the sense that we imagine that we see an assured advantage in a 

 complete separation of fields of work which we sought to arrive at 

 by means of definition. 



But, quite on the contrary, the greatest advances in the sciences 

 are to be made through the union of the results gained by individual 

 research. Not alone through the union of our experiences in special 

 lines, but more especially through the incidence of one science upon 

 the rest, is the richest harvest for all concerned to be gained. This 

 interrelation of the realms of study brings it about that the sciences 

 do not separate from one another, as the classifiers would have it, but, 

 as living streams, change their boundaries, and often unite with each 

 other to form larger units. The final goal, which, to be sure, may 

 never be fully reached, becomes ever clearer: all human knowledge, 

 especially all our knowledge of nature, w y ill become bound together 

 into a great unity. This is the leading thought of my address. 



In order to brevity, I will not attempt to trace out the early paths 

 of plant physiology. I take up the thread of its development at that 

 point where its advance appeared assured, that is, at the time of the 

 revival of art and science. 



The discovery of the New World, and the almost synchronous 

 announcement of the heliocentric world-system, powerfully stimu- 

 lated research; and the invention of printing, which had been given to 

 the world a short time before, made possible the spread of knowledge 

 in a theretofore unthought-of way, so that the conditions preparatory 

 to the advance of science were supplied in a manner as never before. 



Then the spirit was awakened, and bestirred itself in every branch 

 of science. We can quite understand that, as a result of the wide 

 choice of materials for study, a certain irregularity of development 

 in knowledge should appear. But, in spite of such go-as-you-please 

 methods, there grew up a " spirit of the times," more or less unnoticed, 

 which directed the stream of research into more regular channels 

 than the unconstrained impulses to research might lead one to expect. 

 How the genius of single greatness and how the apparently unsus- 

 pected ferments and stimuli of the thought of the times acted upon 

 one another in the struggle up new steeps of knowledge, may not 

 at this time be further discussed. 



At the beginning of the period which I have in mind, the physicist 

 was the first to enrich our knowledge of nature. Mechanics in- 

 cluding the mechanics of the system of worlds formed the point 

 of departure for the studies. Soon followed the discoveries in physics 

 and chemistry, which were not then separated as they became at 

 and after the time of Lavoisier. By the physicists were made the 

 first discoveries in plant physiology, by Mariotte in the seventeenth, 

 and Priestley in the eighteenth century. Priestlev, who was from our 



