1892.] Two Schools of Plant Physiology. 217 



manner in which this is done. On the other hand, oehwend- 

 ener, who treats this question at length, denies our ability at 

 the present condition of botanical knowledge to explain how 

 the water is driven up. The agent he gives, but of the manner 

 in which this agent works, he says we know nothing. 



His treatment rests on a long series of experiments, the last 

 of which were made several years ago and conducted as 

 follows : A forester several miles out of Berlin was authorized 

 by the government to allow the forest under his charge to be 

 invaded for scientific purposes, and a small lodge was built 

 where one of Schwendener's assistants remained for several 

 weeks, in fact about eight weeks, so that the experiments 

 might have an uninterrupted course, the professor going over 

 every few days to perform the manipulations himself, while 

 the assistant remained to watch and report the results. 

 (To be continued) 



