My dear Sir

You have very much rejoiced me by sending me your book on Expression.¹ Reading this book immediately after its appearance I have admired anew your inimitable sagacity and exactness in observing such facts that every one has overlooked as insignificant and which in your hands spread a plenty of light over the most mysterious districts of human understanding. I have been ravished by the evident interpretation you have given of the expression of affects in animals and men, and I have anew been convinced that also psychology will make progress only by leaning on observations of the activity of the soul of animals.— I am very glad to possess this wonderful work from your own hand.

My brother has indeed fertilised in different plants some flowers with strictly their own pollen and other ones by other flowers on the same plant. But in the most cases viz. with Bignonia (Bot. Zeit. 1868. Nr. 39), Tabernaemontana echinata (Bot. Z. 1870. p. 274.), and Abutilon (Jenaische Zeitschrift) he found those plants which are sterile with their own pollen, also sterile with the pollen from distinct flowers on the same plant. Only in Eschscholtzia californica (Bot. Zeit. 1869. Nr. 14) which he found sterile with its own pollen, he was successful in some degree in fertilising it with pollen from a distinct flower on the same plant.²

In order to acquaint you as quickly as possible with the details I send you spare copies of my brothers trials, except Bot. Zeit. 1870. p. 274., of which I do not possess any spare copy.

The number of those plants which exist in two forms, (one more remarkable, more richly visited by insects and never fertilising itself, the other one unsightly, rarely visited by insects but constantly fertilising itself) is certainly much greater than it would appear according to my book.³ I have examined just now the wild Viola tricolor (var. arvensis) and I have found that this plant also constantly fertilises itself (I add a drawing of it)   I suppose that Mr. Bennett in the article May 15, 1873 of the “Nature”, you allude to, has published the same fact, and I would be very glad to become acquainted with this article   I will ask the editor of the Nature for it.⁴

Certainly I shall cultivate several of those plants which exist in the two forms alluded to and I shall try with them in the manner announced by you.⁵

At present I continue ardently to examine the flowers of our wild plants and to research for their fertilisers. Viola tricolor, Myosurus minimus, Calla palustris and Myosotis versicolor are those,⁶ the examination of which has given the most interesting results. In Myosurus the enorm growth of the cone of pistils effects no other thing but the regular self fertilisation of the numerous stigmas by the small number of anthers

Calla palustris is fertilised, like Arum maculatum by very small Dipterous insects, but not by one species but by very different ones; also various Coleoptera are attracted by the white spatha but without finding a recompense. This plant is proterogyne like Arum maculatum, but not so completely.⁷ I cultivate now specimens in my room, in order to decide if they are fertile by self-fertilisation

In Myosotis versicolor the flower opens before having got its blue colour and its ful greatness, by this the style overlooks the anthers affixed to the corolla, and if insects visit now the flower they fertilise it by pollen of other flowers. But a few hours after the opening of the flower the corolla grows in such a degree that the anthers surround closely the stigma and powder it with own pollen.

My brother is very well. During the last years he has spent his leisure time in observing the mimicry of butterflies and the natural history of termites. On the latter subject he will publish some essays, the copies of which I will send you as soon as I receive them. Intending to investigate the genealogy of bees more closely than I have done in my “application of the Darwinian theory to bees” I have begged my brother for sending me specimens of Brasilian bees, and gratifying to my wishes he has not only sent me many Brasilian forms of bees but also acquainted me with a plenty of facts respecting the economy of them.⁸

My dear Sir | yours sincerely | H. Müller

This form of Viola tricolor fertilises itself inevitably, the pollen falling from itself out of the anthers and arriving directly in the opening of the stigma-head, which in flowers perfectly opened is always found fulfilled with pollen grains

The specimens which I have cultivated in my room and guarded during the evolution of the flowers from the visits of insects are quite fertile—will come to maturity in several days.