[The following extract from a letter (February 25, 1864), to Dr. Gray refers to another prediction fulfilled:--"I have of course seen no one, and except good dear Hooker, I hear from no one. He, like a good and true friend, though so overworked, often writes to me.
"I have had one letter which has interested me greatly, with a paper, which will appear in the Linnean Journal, by Dr. Cruger of Trinidad, which shows that I am all right about Catasetum, even to the spot where the pollinia adhere to the bees, which visit the flower, as I said, to gnaw the labellum. Cruger's account of Coryanthes and the use of the bucket-like labellum full of water beats everything: I SUSPECT that the bees being well wetted flattens their hairs, and allows the viscid disc to adhere."]
CHARLES DARWIN TO THE MARQUIS DE SAPORTA.
Down, December 24, 1877.
My dear Sir, I thank you sincerely for your long and most interesting letter, which Ishould have answered sooner had it not been delayed in London. I had not heard before that I was to be proposed as a Corresponding Member of the Institute. Living so retired a life as I do, such honours affect me very little, and I can say with entire truth that your kind expression of sympathy has given and will give me much more pleasure than the election itself, should I be elected.
Your idea that dicotyledonous plants were not developed in force until sucking insects had been evolved seems to me a splendid one. I am surprised that the idea never occurred to me, but this is always the case when one first hears a new and simple explanation of some mysterious phenomenon...I formerly showed that we might fairly assume that the beauty of flowers, their sweet odour and copious nectar, may be attributed to the existence of flower-haunting insects, but your idea, which I hope you will publish, goes much further and is much more important. With respect to the great development of mammifers in the later Geological periods following from the development of dicotyledons, I think it ought to be proved that such animals as deer, cows, horses, etc. could not flourish if fed exclusively on the gramineae and other anemophilous monocotyledons; and Ido not suppose that any evidence on this head exists.
Your suggestion of studying the manner of fertilisation of the surviving members of the most ancient forms of the dicotyledons is a very good one, and I hope that you will keep it in mind yourself, for I have turned my attention to other subjects. Delpino I think says that Magnolia is fertilised by insects which gnaw the petals, and I should not be surprised if the same fact holds good with Nymphaea. Whenever I have looked at the flowers of these latter plants I have felt inclined to admit the view that petals are modified stamens, and not modified leaves; though Poinsettia seems to show that true leaves might be converted into coloured petals. Igrieve to say that I have never been properly grounded in Botany and have studied only special points--therefore I cannot pretend to express any opinion on your remarks on the origin of the flowers of the Coniferae, Gnetaceae, etc.; but I have been delighted with what you say on the conversion of a monoecious species into a hermaphrodite one by the condensations of the verticils on a branch bearing female flowers near the summit, and male flowers below.
I expect Hooker to come here before long, and I will then show him your drawing, and if he makes any important remarks I will communicate with you.