vi PREFACE 



available, including the results of recent research, and we hope that they will 

 stand scrutiny. These descriptions we regard as foundations on which may 

 be built a further study of the group. Our contention is that if a student 

 masters the particulars of structure and life-history in the selected type the 

 related forms will fall naturally into place in their proper perspective. A 

 clearer appreciation of the characteristics of the group as a whole is to be 

 obtained in this way than by the compilation of scraps of information treated 

 comparatively, which gives no coherent account of any one organism in full. 



Based on such a principle this work can obviously make no claim to be a 

 textbook of comparative morphology. The presentation of comparative 

 accounts and the deduction of relationships and of phylogeny we regard as 

 the special function of the lecturer. University lecturing should certainly 

 not, in any case, be devoted to the kind of factual material which it should 

 be the function of a textbook to convey. To place such material in the 

 hands of the student in book form is to free the lecturer to perform his true 

 function, namely to review his subject in the light of his personal knowledge. 



Theoretical problems are not, of course, wholly ruled out of discussion 

 in our descriptions, though they tend to become more prominent in the 

 later chapters than in the strict treatment of types. Above the Gymnosperms, 

 typology becomes impracticable, and in the non-morphological branches, 

 such as Physiology, Ecology and Genetics, theoretical discussions are 

 naturally the order of the day. We have tried in such matters to avoid 

 dogmatism, and we have only occasionally ventured to hint at our own 

 opinions, so that these discussions are also largely factual in the sense that 

 they are presentations of ideas and interpretations which have been formerly 

 advanced or which are actually current. 



Among the general subjects treated we have laid some emphasis on 

 Economic Botany, to which a chapter is devoted. Not many schools of 

 Botany include this subject in their undergraduate courses, but we feel that 

 the omission is one which must soon be remedied. We hope that the day 

 of those who sneered at " merely useful knowledge " has gone by, and the 

 great service which plant science renders to the welfare of mankind will no 

 longer be ignored by scientists under the specious plea of purity, which is 

 so often no more than a wilful blindness to the world around. 



The chapter of Bionomics also demands a word of notice. The word is 

 not familiar in modern textbooks, but it is an expressive and useful term 

 with which to describe the series of phenomena which, for want of a better 

 name, we can call adaptations. In the widest sense the subject-matter is 

 ecological and must be ecologically viewed, but it is sufficiently distinct to 

 be worthy of separate treatment, apart from the fact that its inclusion under 

 Ecology would have swollen that chapter unduly. 



