From T. H. Farrer 28 November 1869
Abinger Hall, | Reigate. (Post Town) | Gomshall (Station) S.E.R.
28 Nov /69
My dear Mr Darwin
I am extremely obliged for the note on Passiflora.1
It quite satisfies me that it wise to delay.2 An ounce of observation is worth a pound of conjecture. And I am in a great puzzle too about names & species, for Hooker tells me that scarcely any of them are true— there has been so much hybridization.3
It would be very interesting to know from your correspondent—4
1. Whether in the species of Passiflora on which he has seen humming birds there are any stiff projections or corners which would make it difficult for a straight stiff object to reach the nectary without boring holes. There are certainly such in those which I have seen.
2. What is the relative position of the humming bird to the anthers or stigmas at the time it is sucking? In none of those which I have seen is there space for a hovering humming bird between the anthers and the entrance to the nectary. This is just one of those things which actual observation alone can tell.
I am sure about the Bee on P. Coerulea, for I have seen it.5
Sincerely yours | T H Farrer
C. Darwin Esqr FRS
I open my note to express a doubt whether one is right in assuming that no bees now visit any flowers. Last Sunday I was marking some plants of Ulex Europæus6 in flower. And I was surprized to find—that whilst in most of those in blossom, not a single flower was deflowered—(ie had an open keel and projecting stigma) there were one or two plants on which almost every flower was thus deflowered— I cut some branches from these two plants as well as from other plants; took off all the flowers then open and placed them in water in a South window (closed). After a week I find all these branches in full blossom—with something like 150 flowers on all—and amongst them only three deflowered. This looks as if some insect still visited—though sparsely and capriciously—some of the flowering plants out of doors. If so the winter flowering plants are more easily explained.
The stout hairy calyx of the Ulex Europæus, is a capital protection to the winter flower, as compared with the thin and comparatively naked calyx of the September Ulex Manus.7
I am delighted with old Sprengel: and his quaint positiveness.8 He is sometimes over-ingenious, it seems to me—but there is a world of suggestion
Agrees that it is wise to delay [publishing?] on Passiflora.
Puts queries he wants CD to send [to Fritz Müller] on bees visiting flowers in winter.