PREFACE 



THE publication of this volume has been delayed owing to war con- 

 ditions, but the delay is the less to be regretted in that it has allowed 

 the inclusion of recent work on the subject. Much of the subject-matter 

 is of common knowledge to lichenologists, but in the co-ordination and 

 arrangement of the facts the original papers are cited throughout. The 

 method has somewhat burdened the pages with citations, but it is hoped 

 that, as a book of reference, its value has been enhanced thereby. The 

 Glossary includes terms used in lichenology, or those with a special licheno- 

 logical meaning. The Bibliography refers only to works consulted in the 

 preparation of this volume. To save space, etc., the titles of books and papers 

 quoted in the text are generally translated and curtailed : full citations will 

 be found in the Bibliography. Subject-matter has been omitted from the 

 index : references of importance will be found in the Table of Contents or 

 in the Glossary. 



I would record my thanks to those who have generously helped me 

 during the preparation of the volume : to Lady Muriel Percy for taking 

 notes of spore production, and to Dr Cavers for the loan of reprints. Prof. 

 Potter and Dr Somerville Hastings placed at my disposal their photographs 

 of the living plants. Free use has been made of published text-figures 

 which are duly acknowledged. 



I have throughout had the inestimable advantage of being able to consult 

 freely the library and herbarium of the British Museum, and have thus been 

 able to verify references to plants as well as to literature. A special debt 

 of gratitude is due to my colleagues Mr Gepp and Mr Ramsbottom for 

 their unfailing assistance and advice. 



A. L. S. I 



London, 



February, 1920 



