6 PLANT PHYSIOLOGY. 



purchasable from the supply companies at a reasonable cost. 

 There is here opened up to the proper combination of physio- 

 logical knowledge and mechanical ingenuity an attractive field 

 for investigation in the invention of less expensive, more 

 manageable, and more logically conclusive experiments for 

 demonstrating the fundamental facts and principles of physi- 

 ology. 



The great danger in the simplification of apparatus is that 

 it will become so crude as to introduce merely mechanical 

 errors, or fail to ensure logical conclusiveness in results. Since 

 a great part of the value of such a course consists in a training 

 in the experimental habit, the greatest care should be taken 

 to safeguard the logical quality, as well as the quantitative cor- 

 rectness, of the experiments, and none should be admitted 

 which do not fairly meet these requirements. 



It may also appear that some of the experiments here 

 recommended are of too elementary a character for this course, 

 and are such as the students must have tried, or at least have 

 seen tried, earlier in their studies. It seems best, however, to 

 make the course complete in itself. Repetition has its advan- 

 tages, and even the simplest experiments take on a new mean- 

 ing when tried by the students themselves in their proper 

 connections ; while in any case it is always possible for the 

 teacher to replace the simpler by more complex and exact 

 ones. 



The general belief that elaborate apparatus is necessary for 

 good student work in plant physiology is of course the reason 

 for the persistence in places of the older method of conducting 

 physiological courses. This method, in its extreme, is that of 

 providing the laboratory with a piece of each of the approved 

 purchasable kinds of apparatus, and assigning to each student 

 a distinct topic for thorough study; the topics are usually 

 changed two or three times in the term, and each student is 

 supposed to keep in touch with, and to profit by, the work of 

 his classmates. After experience of this individual system as 

 a student, and for several years as a teacher, I am convinced 



