From T. H. Farrer   29 June 1870

My dear Mr Darwin

I have at last got a flower of Passiflora Princeps.¹ You were quite right, as you seem always to be   The lower or inner coronas, or whatever they are, which cover the nectary, neither fit close to the style, nor lap over one another so as to prevent the entrance of a stiff object. There are wide gaps by which a pin does get to the bottom and comes out covered with nectar. But the style is very long: the flower sub-erect: and, so far as I can see, the anthers and stigmas do not droop down as in P. Caerulea. The consequence is that the distance between these organs and the nectary & their relative position is such that a bee on the top of the outer coronas would not touch them. Add to this that the two outer coronas are very little developed: and that the third closes round the style so as to make it an inch from the entrance to the bottom of the nectary— I think with all this we have a correlation of parts suited for Humming birds & not for Bees.—though not exactly the correlation I noted in the others.²

I will certainly come and see you as you so kindly suggest—but am very busy till the Session is over—which I find the best thing. It is the leisure & the tired hours which are difficult to bear.³

Sincerely yours | T H Farrer

We have been deeply interested in watching the wonderful motions of Passifloras in climbing. They seek & find & hold on & pull up like an animal