Dear Sir

Owing to M^r Russell not having found my proper address & his subsequent absence on the Continent, I received the present of your magnificent work with its excellent illustrations, only about a week ago.¹ I have now read it with much interest, & am astonished that such a work could have been prepared at Sydney. I have been particularly interested by your account of the movements of Pterostylis & Caladenia.² Do you think it possible that the calli on the labellum are gnawed or sucked by insects?³ A careful examination of the flowers from which the pollinia have been removed by insects, would be well worth making. I daresay you have seen a good paper on the former genus in a late vol of the N. Zealand Institute.⁴ I have been even more interested about the closed flowers of Thelymitra, as the case is closely analogous to the equally inaccessible one of the Bee Ophrys in Europe.⁵ I suppose you have few coadjutors, but it would be well to ascertain whether the flowers are closed during years when the seasons are very different, & in all parts of the plant’s range. I will venture to make one other suggestion; viz with sterile species like Dendrobium hillii to try the effects of pollen taken from a distinct seedling plant, in accordance with the observations of Fritz Müller.⁶ I have found it almost necessary to observe insects at work to understand the meaning of the parts in orchids & on this head I see that you are a disbeliever.⁷ From not having been able to act in this manner I blundered about Cypripedium;⁸ but I do not think I have erred about the nectary of Angræcum, & Wallace has given the case of a sphinx with proboscis of sufficient length.⁹

With my best thanks & good wishes for your future success | I remain dear Sir | Yours faithfully | Ch. Darwin