1 88 1-2.] BOTANICAL LETTERS. 351 



Mr. Torbitt tells me that he still (1887) succeeds in raising 

 varieties possessing well-marked powers of resisting disease ; 

 but this immunity is not permanent, and, after some years, the 

 varieties become liable to the attacks of the fungus.] 



The Kew Index of Plant-Names, or ' Nomenclator 



botanicus darwinianus '. 



[Some account of my father's connection with the Index of 

 Plant-names now (1887) in course of preparation at Kew will 

 be found in Mr. B. Daydon Jackson's paper in the ' Journal of 

 Botany,' 1887, p. 151. Mr. Jackson quotes the following state- 

 ment by Sir J. D. Hooker : — 



"Shortly before his death, Mr. Charles Darwin informed 

 Sir Joseph Hooker that it was his intention to devote 

 a considerable sum of money annually for some years in 

 aid or furtherance of some work or works of practical 

 utility to biological science, and to make provisions in his 

 will in the event of these not being completed during his 

 lifetime. 



" Amongst other objects connected with botanical science, 

 Mr. Darwin regarded with especial interest the importance of 

 a complete index to the names and authors of the genera and 

 species of plants known to botanists, together with their 

 native countries. Steudel's ' Nomenclator' is the only existing 

 work of this nature, and although now nearly half a century 

 old, Mr. Darwin had found it of great aid in his own re- 

 searches. It has been indispensable to every botanical insti- 

 tution, whether as a list of all known flowering plants, as an 

 indication of their authors, or as a digest of botanical 

 geography." 



Since 1840, when the 'Nomenclator' was published, the 

 number of described plants may be said to have doubled, so 



