INTRODUCTION. 5 



while precise quantitative results, although the only logical end 

 for the investigator, would be quite lost upon the beginner. 

 This has long been recognized in Physics, where great simpli- 

 fication of methods and appliances has been effected to the 

 decided profit of the educational interests of the subject. It is 

 not, however, to be inferred that, since it is the qualitative 

 rather than the quantitative aspect of the results that is valuable 

 in such a course as this, therefore quantitative methods are not 

 those to be employed. On the contrary, the exact quantitative 

 method and spirit are scientifically and educationally the best, 

 one may even say the only permissible, for even qualitative 

 work ; and it is entirely in this method and spirit that the 

 present course is intended to be carried on. Simple, even 

 crude, though some of these appliances are, there is no one of 

 them which, correctly used, gives other than the correct kinds 

 of results, and usually with approximate accuracy. 



In most minds the practical study of plant physiology is 

 associated with a necessity for the possession of the many and 

 costly appliances developed by investigators for securing pre- 

 cision in quantitative researches. In my own experience, 

 however, which is confirmed by the testimony of other 

 teachers, I have found that not only are such appliances quite 

 unnecessary for sound physiological education, but the}- are, 

 owing to difficulties of manipulation and related reasons, 

 actually no better than the simpler though less exact apparatus, 

 even if they are equal to them. For investigation, in which 

 one can afford to use nothing less than the very best, the elab- 

 orate pieces are usually necessary ; it is also an advantage in 

 elementary courses to have some of them at hand for illustra- 

 tion and occasional demonstration ; but further than this they 

 may be entirely dispensed with. There has been for some 

 time a movement towards this simplification of apparatus and 

 methods, the leading contributors to which are mentioned in 

 the Preface, but much still remains to be done. No doubt the 

 subject will gradually work itself out in the form of a series of 

 standard simple appliances giving results of fair accuracy, and 



