i868 i8Si] GALLS 427 



They have always seemed to me profoundly interesting. Letter 757 

 Many years ago I began (but failed for want of time, strength, 

 and health, as on infinitely many other occasions) to experi- 

 mentise on plants, by injecting into their tissues some 

 alkaloids and the poison of wasps, to see if I could make 

 anything like galls. If I remember rightly, in a few cases 

 the tissues were thickened and hardened. I began these 

 experiments because if by different poisons I could have 

 affected slightly and differently the tissues of the same plant, 

 I thought there would be no insuperable difficulty in the 

 fittest poisons being developed by insects so as to produce 

 galls adapted for them. Every character, as far as I can see, 

 is apt to vary. Judging from one of your sentences you will 

 smile at this. 



To any one believing in my pangenesis (if such a man 

 exists) there does not seem to me any extreme difficulty in 

 understanding why plants have such little power of regenera- 

 tion 1 ; for there is reason to think that my imaginary 

 gemmules have small power of passing from cell to cell. 



Forgive me for scribbling at such unreasonable length ; 

 but you are to blame for having interested me so much. 



P.S. Perhaps you may remember that some two years 

 ago you asked me to lunch with you, and proposed that I 

 should offer myself again. Whenever I next come to 

 London, I will do so, and thus have the pleasure of seeing 

 you. 



To W. Thiselton-Dyer. Letter 758 



The Power of Movement in Plants was published early in November, 

 1880. Sir W. Thiselton-Dyer, in writing to thank Darwin for a copy 

 of the book, had (Nov. 2oth) compared a structure in the seedling 

 Weluuitschia with the " peg " of Curcurbita (see Power of Movement, 

 p. 102). Dyer wrote : "One peculiar feature in the germinating embryo 

 is a lateral hypocotyledonary process, which eventually serves as an 

 absorbent organ, by which the nutriment of the endosperm is conveyed 

 to the seedling. Such a structure was quite new to me, and Bower and 

 I were disposed to see in it a representative of the foot in Sdaginella^ 

 when I saw the account of Flahault's 'peg.' ;; Flahault, it should be 



1 On regeneration after injury, see Massart, La Cicatrisation chez les 

 Vegetaux, in Vol. 57 (1898) of the Me moires Couronnes, published by 

 the Royal Academy of Belgium. An account of the literature is given 

 by the author. 



