PREFACE 



The investigations embodied in this Memoir were begun in the 

 autumn of 1904, with the intention of making them a minor problem 

 during a year's residence at the New York Botanical Garden. On 

 account of the scarcity of radium the work progressed slowly, for it 

 was seldom that more than one or two experiments could be con- 

 ducted simultaneously. When it became certain that the facilities of 

 the Garden laboratories would be available for an indefinite period, 

 other work was made secondary to the radium problem, for the rela- 

 tively large quantities of radium and radium preparations placed at 

 my disposal created an opportunity too valuable to let pass unim- 

 proved. 



Chapter I. contains, in concise, non-technical language, informa- 

 tion that is widely scattered in publications, many of which are not 

 easily accessible or familiar to botanists. This information, however, 

 is absolutely essential in order to understand the discussions that fol- 

 low, and it was deemed advisable to include it. 



The problem was originally suggested by Dr. William J. Gies, 

 Consulting Chemist of the New York Botanical Garden, and it is a 

 pleasure to acknowledge his helpful suggestions during the earlier 

 progress of the work. 



The investigations would not have been possible had it not been 

 for the munificent liberality of Mr. Hugo Lieber, of the firm of H. 

 Lieber & Co., of New York City. Mr. Lieber has freely placed at 

 my disposal some $3,000 to $4,000 worth of standard preparations 

 of the purest radium bromide yet obtained, as well as weaker prepara- 

 tions of radium, polonium, and radio-tellurium. As stated in detail in 

 the pages that follow, he has devised apparatus, and made other 

 apparatus at my suggestion, without which many of the experiments 

 could not have been performed. It is not possible adequately to ex- 

 press in words my sincere gratitude to Mr. Lieber, not only for his 

 great liberality, but also for the kindly interest he has maintained in 

 the research throughout its entire progress. 



C. Stuart Gager. 



New York Botanical Garden. 



