CHAPTER III 



THE SCOPE OF THIS BOOK 



It is interesting to look back upon some of the comments 

 made by reviewers of the first edition. The book was origin- 

 ally written for chemists, and after the second chapter it 

 assumed and still assumes the reader to have a knowledge of 

 chemistry at least equal to that of pass degree standard. 

 Chapter XIII, which one reviewer justly said could only give 

 the layman a headache, introduces the indole group of 

 compounds, but ignores most of the phenyl compounds, with 

 which the reader of that chapter can be expected to be suffi- 

 ciently familiar. Few chemists, except specialists in some 

 branches of organic chemistry, know much about the indole 

 (benz-pyrrole) nucleus, though they all know the phenyl ring. 

 Hence the chemical explanations start from the phenyl ring, 

 and no attempt is made to simplify organic chemistry further 

 by introducing explanations couched in terms the non- 

 chemist might possibly understand but of which he would 

 probably lose the thread long before he had an idea of the 

 meaning of the structural formula of benz-pyrrole. 



Chemistry, like everything else, has to be learnt; but this 

 book is not the place to teach its elements. 



Originally the book contained no plant physiology, and 

 some plant physiologists who reviewed the book apparently 

 concluded that it was therefore a quite unintelligible and 

 peculiarly useless piece of work. Another praised it (on the 

 whole) for what it was, but devoted a good share of his space 

 to regretting that the book did not set forth an explanation 

 of the action of all growth-promoting and growth-regulating 

 substances in every sphere. Such an explanation neither I 



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