PREFACE 



This is the last section of the " Flora of Tropical Africa " which will 

 be issued under my editorship. The control and supervision necessary 

 in an undertaking of the kind cannot be properly exercised except at 

 the headquarters of its preparation. Some degree of uniformity must 

 at least be aimed at in the work of different contributors. Questions 

 will consequently arise on which the editor must give a decision: 

 difficulties which are readily solved by personal discussion are not 

 disposed of so easily by correspondence. 



The preparation of this section has been protracted. When I retired 

 from the Directorship of Kew in 1905 much of the material available 

 had been worked up by my indefatigable contributor, Mr. J. G. 

 Baker, F.R.S. The continuous access of fresh collections had in the 

 meantime largely added to it. In fact the general position with regard 

 to the Flora resembles the " Curve of 'Pursuit," in which the pursuer 

 has to change his direction constantly in the attempt to overtake his 

 elusive quarry. In the case of the smaller orders Mr. Baker's advanced 

 years made it necessary to entrust the necessary additions to other 

 hands. The Eiqyhorhiacece were not so easily disposed of. This vast 

 family will probably prove to supply the dominant constituent of tropical 

 forests. In view of the large access of fresh material and of what had 

 been worked out by Continental botanists it was necessary to recast 

 entirely what had been prepared. This task was generously undertaken 

 by my successor Lt.-Col. Sir David Prain, F.R.S., and though my 

 name stands on the title-page of the volume, its accomplishment and the 

 merit which attaches to it must for the most part be attributed to his 

 indefatigable energy and critical insight. Mr. J. Hutchinson collabo- 

 rated with him, and Mr. N. E. Brown, A.L.S., who finds a peculiar 

 fascination in the study of succulent plants, the difficulties of which 

 most botanists find deterrent, undertook the genus Euphorbia. 



The present section thus disposes of all that was in view when I 

 retired from Kew. The " Flora of Tropical Africa " differs from other 



