PREFACE 



IX 



not quite, in Chestertonian phrase, to get the heavens into our head, but 

 nevertheless the task of compression is difficult enough. For the imper- 

 fections of what we have accomplished in this way, we can only ask for 

 the kindly indulgence of those who from their specialist knowledge could 

 without doubt have written their own particular sections very much better. 

 It was because we felt that the work should be a balanced survey that we 

 attempted to write the whole of it ourselves. 



We wish to thank our publishers for allowing us to illustrate the text 

 so fully. The illustrations consist largely of photographs, most of which 

 we have taken ourselves from material in our own collections or from those 

 of the Department of Botany. A certain number have been obtained through 

 the kindness of friends or from commercial firms, acknowledgment of which 

 is made where they are reproduced. Some illustrations from " Biology for 

 Medical Students," by C. C. Hentschel and W. R. Ivimey-Cook, published 

 by Messrs Longmans, Green and Co., have also been incorporated. 



We have also received help in other directions, notably from Professor 

 R. J. Tabor, to whom we owe some ver\' valuable criticisms and suggestions. 

 Lastly we wish to thank Mrs Ivimey-Cook for extensive help in typing and 

 proof correcting, and Mrs McLean for the compilation of the Index, both 

 laborious tasks which were cheerfully undertaken. 



R. C. McLEAN. 



W. R. IVIMEY-COOK. 



The University of Wales, 



University College, Cardiff, 

 March 1949. 



I A 



