To Fritz Müller   23 February 1881

My dear Sir

Your letter has interested me greatly, as have so many during many past years. I thought that you w^d. not object to my publishing in Nature some of the more striking facts about the movements of Plants, with a few remarks added to show the bearing of the facts. The case of the Phyllanthus which sometimes turns up its leaves on the wrong side is most extraordinary & ought to be further investigated.¹

Do the leaflets sleep on the following night in the usual manner? Do the same leaflets on successive nights move in the same strange manner? I was particularly glad to hear of the strongly marked cases of paraheliotropism.—² I shall look out with much interest for the publication about the Figs. The creatures which you sketch are marvellous & I sh^d not have guessed that they were Hymenoptera.³ Thirty or forty years ago I read all that I c^d. find about caprification & was utterly puzzled.⁴ I suggested to D^r. Crüger in Trinidad to investigate the wild figs, in relation to their cross-fertilisation, & just before he died he wrote that he had arrived at some very curious results, but he never published, as I believe on the subject.—⁵

I am extremely glad that the inundation did not so greatly injure your scientific property; though it would have been a real pleasure to me to have been allowed to have replaced your scientific apparatus.⁶ I do not believe that there is anyone in the world who admires your zeal in science & wonderful powers of observation more than I do.— I venture to say this, as I feel myself a very old man, who probably will not last much longer.

Believe me, my dear Sir | Yours very sincerely | Ch. Darwin

P.S. With respect to Phyllanthus, I think that it w^d. be good experiment to cut off most of the leaflets on one side of petiole, as soon as they are asleep & vertically dependent.— When the pressure is thus removed, the opposite leaflets will perhaps bend beyond their vertically dependent position; if not, the main petiole might be a little twisted so that the upper surfaces of the dependent & now unprotected leaflets sh^d. face obliquely the sky, when the morning comes. In this case diaheliotropism would perhaps conquer the ordinary movements of the leaves when they awake & resume their diurnal horizontal position.— As the leaflets are alternate & as the upper surface will be somewhat exposed to the dawning light it is perhaps diaheliotropism which explains your extraordinary case.⁷