i860.] on plants of the same species.' 299 



.... In the spring I must get you to look for long pistils and 

 short pistils in the rarer species of Primula and in some allied 

 Genera. It holds with P. Sinensis. You remember all the 

 fuss I made on this subject last spring ; well, the other day 

 at last I had time to weigh the seeds, and by Jove the plants 

 of primrose and cowslip with short pistils and large grained 

 pollen * are rather more fertile than those with long pistils, 

 and small-grained pollen. I find that they require the action 

 of insects to set them, and I never will believe that these 

 differences are without some meaning. 



Some of my experiments lead me to suspect that the large- 

 grained pollen suits the long pistils and the small-grained 

 pollen suits the short pistils ; but I am determined to see if I 

 cannot make out the mystery next spring. 



How does your book on plants brew in your mind ? Have 

 you begun it ? . . . 



Remember me most kindly to Oliver. He must be 

 astonished at not having a string of questions, I fear he will 

 get out of practice ! 



[The Primula- work was finished in the autumn of 1 861, and 

 on Nov. 8th he wrote to Sir J. D. Hooker : — 



" I have sent my paper on dimorphism in Primula to the 

 Linn. Soc. I shall go up and read it whenever it comes on ; 

 I hope you may be able to attend, for I do not suppose many 

 will care a penny for the subject." 



With regard to the reading of the paper (on Nov. 21st), he 

 wrote to the same friend : — 



" I by no means thought that I produced a " tremendous 

 effect " in the Linn. Soc, but by Jove the Linn. Soc, pro- 

 duced a tremendous effect on me, for I could not get out of 

 bed till late next evening, so that I just crawled home. I 

 fear I must give up trying to read any paper or speak ; it is 

 a horrid bore, I can do nothing like other people. 



* Thus the plants which he male condition were more produc- 

 imagined to be tending towards a tive than the supposed females. 



