Dear Sir

Your letter, as every one you have written, has greatly interested me.² If you can show that certain individual Passifloras, under certain known or unknown conditions of life, have stigmas capable of fertilisation by pollen from another species, or from another individual of its own species, yet not by its own individual pollen, (its own individual pollen being proved to be good by its action on some other species) you will add a case of great interest to me; & which in my opinion would be quite worth your publication. I always imagined that such recorded cases must be due to unnatural conditions of life; & think I said so in Origin.³ I am not sure that I understand your result, whether it means what I have above obscurely expressed. If you can prove the above, do publish; but if you will not publish I earnestly beg you to let me have the facts in detail; but you ought to publish for I may not use facts for years.—⁴

I have been much interested by what you say on the Rostellum exciting pollen to protrude tubes;⁵ but are you sure that the rostellum does excite them? would not tubes protrude if placed on part of column or base of petals &c., near to the stigma?— Please look at Cottage Gardener (or J. of Hort) to be published tomorrow week for letter of mine, in which I venture to quote you, & in which you will see curious fact about unopened orchid flowers setting seed in W. Indies.⁶ D^r. Cruger attributes protrusion of tubes, to ants carrying stigmatic secretion to pollen; but this is mere hypothesis.⁷ Remember pollen-tubes protrude within anther in Neottia nidus-avis—⁸ I did think it possible or probable that perfect fertilisation might have been effected through rostellum.

What a curious case your Gongora must be:⁹ could you spare me one of largest capsule: I want to estimate number of seed, & try my hand if I can make them grow. This, however, is foolish attempt; for D^r. Hooker who was here a day or two ago;¹⁰ says they cannot at Calcutta, & yet imported species have seeded & have naturally spread on to the adjoining trees!

D^r. Cruger thinks I am wrong about Catasetum; but I cannot understand his letter:¹¹ he admits there are 3 forms in 2 species; & he speaks as if the sexes were separate in some & that others were hermaphrodite; but I cannot understand what he means.— He has seen lots of great Humble-bees buzzing about the flowers with the pollinia sticking to their backs! Happy man!!. I have the promise but not yet surety of some curious results with my homorphic seedling Cowslips: these have not followed rule of Chinese Primula; homorphic seedlings from short-styled parent have presented both forms, which disgusts me.—¹²

You will see that I am better; but still greatly fear that I must have compulsory holiday.

With sincere thanks & hearty admiration at your powers of observation.— Dear Sir | Yours sincerely | C. Darwin

My poor P. Scotica, look very sick, which you so kindly sent me.—¹³