PREFACE. 



I HAVE placed the essays in the order in 

 which they will be found in accordance with 

 the dates when they were first published. As 

 I wish to acknowledge to whom I am indebted 



o 



for the permission to reproduce them, and also 

 wish to refer my readers to the originals in 

 case they should wish to consult them, 1 

 cannot do better than to thank the journals, 

 and to give the necessary list at the same 

 time, as follows : 



(1) Dr. Axel Preyer's article will be found 

 in Der Tropenpflanzer, No. 4, of April, 1901, 

 pp. 157-173. The translation, made by my 

 brother Victor and M. Ulrich Hugentobler, 

 originally appeared in Tropical Life. 



(2) Dr. Oscar Loew's essay is taken from 

 Bulletin No. 1093 f th e United States 

 Department of Agriculture (Office of Experi- 

 ment Stations), and first appeared in the 

 Annual Report of the Porto Rico Agricultural 

 Experiment Station for 1907. 



(3) Dr. Fickendey's (Director of the 

 Experiment Station, Victoria, Cameroons, 

 German West Africa) was taken from 

 Der Tropenpflanzer, No. 2, of February, 

 1909, pp. 87-90 ; and I am indebted to 



