PREFACE 



In the diagnosis of each genus the essential peculiarities distinguishing it from 

 other genera are given in the first paragraph. In the next follows a sketch of more 

 general characters not necessarily confined to it. 



Orchids are perhaps the most elusive of all flowering plants, and many a theory 

 tentatively advanced or dogmatically laid down has been proved by time to be 

 erroneous. One must enter the shrine of their closely guarded secrets with an open 

 mind ready to discard the most cherished preconceived ideas if necessary. 



A viewer specially made to enable readers to see Herr Pfeiffer's photographs with 

 stereoscopic clearness and perspective (but not adapted for ordinary stereographs) 

 may be obtained from the Thornton-Pickard Manufacturing Co. Ltd., Altrmcham, 

 Cheshire, price is. 6d. each plus ^d. postage in the United Kmgdom. 



I desire to express sincere thanks to the foUowing: Prof. Oakes Ames of Harvard 

 University, U.S.A., for help in respect of Spiranfhes V^ommxpffiana and tor text- 

 fieure qa. Sir Maurice Abbot Anderson for interesting specimens of Dorsetshire 

 orchids. Messieurs R. Benoist and L. Berland of the Pans Museum d Histoire 

 Naturelle for identifying insects taken visiting orchids. Mile A. Canius for much 

 helpful information and for permission to reproduce text-figures from the Iconographie 

 desOrchidees d'Europe. The late Mr E. N. Carrothers of Belfast for observations on 

 Irish orchids. Mrs E. Coleman of Blackburn, Victoria, for notes on the pollination 

 of Australian orchids. Dorothy, Countess of Cranbrook, for specimens of rare forms 

 of orchids. The late Dr G. C. Druce, F.R.S., for valuable information and rare speci- 

 mens of British orchids. Mr T. A. Dymes, F.L.S., whose studies of the seeds of 

 orchids were of great interest. Colonel G. H. Evans, F.L S., and Mrs Evans for 

 active help in discovermg the visiting insects of several orchids Prof. M L. Fernald 

 of Harvard Umversity, U.S.A., for aid in identifying the Irish Sptranthes with the 

 American S. Koman^offiana. Colonel C. T. Green for the photographs on PI. C. 

 Mr P M. Hall for valuable help in the field. Prof. J. W. Heslop Harrisoii, F.R S., 

 for notes on chromosomes and rare Durham orchids. Monsieur Houzeau de Lehaie 

 for information as to British orchids growing also in Belgium. Dr Gottfried KeUer 

 of Aarau, who told us of many orchid stations in Switzerland and Italy. The late 

 Mr Wilfrid Matheson for observations on Somersetshire orchids. Monsieur Meslin 

 of Caen, who discovered Bpipactis dmensis Godf. on the French coast Mr H 

 Mousley of Ontario for notes on Canadian orchids. Herr F. Pfeiffer-Wellheim of 

 Vienna for permission to reproduce the beautiful stereographic photographs on 

 Pis A D E F Prof. E.B.Poulton,F.R.S., for the determination of visiting insects. 

 Monsieur' M. Pouyanne, first discoverer of the method of PoUif ^^^^^ f Ophrjs, for 

 information as to the fertilisation of Algerian orchids. Dr A. B. Rendle, F.R.S., for 

 help and encouragement and for publishing much of our work m the Journal oj 



