The enclosed letter from that excellent observer, Fritz Müller, contains some miscellaneous observations on certain plants and insects of South Brazil, which are so new and curious that they will probably interest your naturalist readers.2 With respect to his case of bees getting their abdomen dusted with pollen while gnawing the glands on the calyx of one of the Malpighiaceæ, and thus effecting the cross-fertilisation of the flowers, I will remark that this case is closely analogous to that of Coronilla recorded by Mr. Farrer in your journal some years ago, in which parts of the flowers have been greatly modified, so that bees may act as fertilisers while sucking the secretion on the outside of the calyx.3 The case is interesting in another way. My son Francis has shown that the food-bodies of the Bull’s-horn Acacia, which are consumed by the ants that protect the tree from its enemies (as described by Mr. Belt), consist of modified glands; and he suggests that aboriginally the ants licked a secretion from the glands, but that at a subsequent period the glands were rendered more nutritious and attractive by the retention of the secretion and other changes, and that they were then devoured by the ants.4 But my son could advance no case of glands being thus gnawed or devoured by insects, and here we have an example.
With respect to Solanum palinacanthum, which bears two kinds of flowers on the same plant, one with a long style and large stigma, the other with a short style and small stigma, I think more evidence is requisite before this species can be considered as truly heterostyled, for I find that the pollen-grains from the two forms do not differ in diameter.5 Theoretically it would be a great anomaly if flowers on the same plant were functionally heterostyled, for this structure is evidently adapted to insure cross-fertilisation of distinct plants. Is it not more probable that the case is merely one of the same plant bearing male flowers through partial abortion, together with the original hermaphrodite flowers? Fritz Müller justly expresses surprise at Mr. Leggett’s suspicion that the difference in length of the pistil in the flowers of Pontederia cordata of the United States is due to difference of age; but since the publication of my book Mr. Leggett has fully admitted, in the Bulletin of the Torrey Botanical Club, that this species is truly heterostyled and trimorphic.6 The last point on which I wish to remark is the difference between the males and females of certain butterflies in the neuration of the wings, and in the presence of tufts of peculiarly-formed scales. An American naturalist has recently advanced this case as one that cannot possibly be accounted for by sexual selection.7 Consequently, Fritz Müller’s observations which have been published in full in a recent number of Kosmos, are to me highly interesting, and in themselves highly remarkable.8
Charles Darwin
Down, Beckenham, Kent, November 21
Please cite as “DCP-LETT-11245,” in Ɛpsilon: The Charles Darwin Collection accessed on