My dear Sir

Owing to all sorts of interruptions and to my reading German so slowly, I have read only to p. 88 of your book; but I must have the pleasure of telling you how very valuable a work it appears to me.¹ Independently of the many original observations, which of course form the most important part, the work will be one of the highest use as a means of reference to all that has been done on the subject. I am fairly astonished at the number of species of insects, the visits of which to different flowers you have recorded. You must have worked in the most indefatigable manner. About half a year ago the editor of Nature suggested that it would be a grand undertaking if a number of naturalists were to do what you have already done on so large a scale with respect to the visits of insects.² I have been particularly glad to read your historical sketch, for I had never before seen all the references put together.³ I have sometimes feared that I was in error when I said that C. K. Sprengel did not fully perceive that cross-fertilization was the final end of the structure of flowers; but now this fear is relieved, and it is a great satisfaction to me to believe that I have aided in making his excellent book more generally known.⁴ Nothing has surprised me more than to see in your historical sketch how much I myself have done on the subject, as it never before occurred to me to think of all my papers as a whole. But I do not doubt that your generous appreciation of the labours of others, has led you to over estimate what I have done.

With very sincere thanks, and respect | Believe me | Yours faithfully | Charles Darwin

P.S.— I have mentioned your book to almost everyone who, as far as I know, cares for the subject in England; and I have ordered a copy to be sent to our Royal Society.⁵