i38i.] MISCELLANEOUS BOTANICAL LETTERS. 517 



to the direct action of conditions, but Hoffmann's paper has 

 staggered me. Perhaps hundreds of generations of exposure 

 are necessary. It is a most perplexing subject. I wish I 

 was not so old, and had more strength, for I see lines of re- 

 search to follow. Hoffmann even doubts whether plants 

 vary more under cultivation than in their native home and 

 under their natural conditions. If so, the astonishing varia- 

 tions of almost all cultivated plants must be due to selection 

 and breeding from the varying individuals. This idea crossed 

 my mind many years ago, but I was afraid to publish it, as I 

 thought that people would say, " how he does exaggerate the 

 importance of selection." 



I still must believe that changed conditions give the im- 

 pulse to variability, but that they act in most cases in a very 

 indirect manner. But, as I said, it is a most perplexing prob- 

 lem. Pray forgive me for writing at such length ; I had no 

 intention of doing so when I sat down to write. 



I am extremely sorry to hear, for your own sake and for 

 that of Science, that you are so hard worked, and that so 

 much of your time is consumed in official labour. 

 Pray believe me, dear Professor Semper, 

 Yours sincerely, 



Charles Darwin. 



Galls. 



[Shortly before his death, my father began to experiment- 

 ise on the possibility of producing galls artificially. A letter 

 to Sir J. D. Hooker (Nov. 3, 1880) shows the interest which 

 he felt in the question : — 



" I was delighted with Paget's Essay ; * I hear that he has 

 occasionally attended to this subject from his youth .... 

 I am very glad he has called attention to galls : this has 

 always seemed to me a profoundly interesting subject ; and if 

 I had been younger would take it up." 



His interest in this subject was connected with his ever- 



* ' Disease in Plants,' by Sir James Paget. — See Gardeners' Chronicle, 

 18S0. 



