VI PREFACE. 



to the identification of the substance in the tissues of the 

 plant itself. It has been difficult to decide just how much 

 to give and how much to withhold in this part of the 

 course, but I regard the contents of Chapter II. as repre- 

 senting the minimum amount of work of this kind which 

 should be done by the student. 



In the second section (Physiology) I have outlined a 

 thoroughly practical, but on the whole easy and elemen- 

 tary, course of Plant Physiology. In this course there are 

 very few experiments that cannot be performed without the 

 use of expensive pieces of apparatus. Before beginning 

 this part of the work, the student should refer to 20 to 

 25 in Chapter I., noting carefully the general instructions 

 there given regarding apparatus and methods. 



I have begun Chapter IV. with the study of seeds and 

 seedlings, because (1) the structure of seeds follows most 

 naturally upon the floral histology and embryology given 

 at the end of Chapter III., (2) I cannot suggest any better 

 method of starting systematic work in Physiology than 

 that of studying the germination of seeds, and (3) the 

 growing of seedlings provides at once a stock of material 

 especially well suited for many experiments. 



While much good work may be done with makeshift 

 apparatus, teachers and students should realise that in 

 many cases it is simply waste of time to fit up the make- 

 shift apparatus. In the teaching of Plant Physiology a 

 certain amount of special ready-made apparatus is just as 

 essential as in the teaching of Physics. The botanical 

 teacher should at any rate have at his disposal the chief 

 pieces in Ganong's set of Normal Apparatus for Plant 

 Physiology made by the Bausch and Lomb Optical Com- 

 pany. 



In Section III. on Life Histories, I have not used pre- 



