My dear Monsieur de Candolle,

It was extremely kind of you to write me so long and valuable a letter, the whole of which deserves careful consideration. I have been particularly pleased at what you say about the new terms used, because I have often been annoyed at the multitude of new terms lately invented in all branches of Biology in Germany; and I doubted much whether I was not quite as great a sinner as those whom I have blamed.¹ When I read your remarks on the word ‘purpose’ in your ‘Phytographie’, I vowed that I would not use it again; but it is not easy to cure oneself of a vicious habit.² It is also difficut for any one who tries to make out the use of a structure to avoid the word purpose. I see that I have probably gone beyond my depth in discussing plurifoliate & unifoliate leaves; but in such a case as that of Mimosa albida, where rudiments of additional leaflets are present we must believe that they were well developed in the progenitor of the plant. So again when the first true leaf differs widely in shape from the older leaves, & resembles the older leaves in allied species, is it not the most simple explanation that such leaves have retained their ancient character, as in the case of the embryos of so many animals?³

Your suggestion of examining the movements of vertical leaves with an equal number of stomata on both sides, with reference to the light, seems to me an excellent one and I hope that my son Francis may follow it up.⁴ But I will not trouble you with any more remarks about our book.

My son will write to you about the diagram.⁵

Let me add that I shall ever remember with pleasure your visit here last autumn,⁶ & I remain dear Monsieur De Candolle

Yours very sincerely | Charles Darwin