PREFACE 9 



some serious knowledge of the specific structures, 

 activities and evolution of plants is an essential part 

 of a broad biological foundation. There are things 

 about life as a whole that we can only learn from 

 plants, and there are others which some knowledge 

 of plants helps us to understand far more completely. 

 The ideal course in elementary biology would un- 

 doubtedly be given by a teacher dealing with both 

 plants and animals. Unfortunately, the differentiation 

 of botany and zoology has gone much too far to 

 make it possible to find or to employ such a teacher 

 in most existing British universities. The Cambridge 

 course attempts a compromise which approaches, 

 though it cannot attain, this ideal, for the introductory 

 lectures deal with animals as well as with plants, 

 while plants as well as animals are freely used as 

 illustrations in the concluding lectures of the zoological 

 portion, which are concerned with heredity and 

 evolution. 



If all school children were taught some biology, 

 as they certainly should be, and this were on well 

 considered and recognised lines, the task of the 

 university teacher would be more straightforward 

 and more profitable : he could give his students a 

 far better training in the time at his disposal. As it 

 is he is bound to assume that they know nothing 

 of biology and very little of chemistry and physics. 

 A rudimentary knowledge of inorganic chemistry 

 is, however, assumed in this book, and this is now 

 fairly common among students entering the university. 



The chief points in which this book differs from most 

 works of similar scope are the following. First of 

 all much more space is devoted to biological facts 



