My dear Sir

I do not know how to express you my deep heartfelt gratitude for the generous offer, which you made to my brother on hearing of the late dreadful flood of the Itajahy. From you, dear Sir, I should have accepted assistance without hesitation, if I had been in need of it; but fortunately, though we had to leave our house for more than a week and on returning found it badly damaged, my losses have not been very great.—¹

I must thank you also for your wonderful book on the movements of plants, which arrived here on new year’s day.² I think, nobody else will have been delighted more, than I did, with the results, which you have arrived at by so many admirably conducted experiments and observations; since I observed the spontaneous revolving movement of Alisma, I had seen similar movements in so many and so different plants, that I felt much inclined to consider spontaneous revolving movement or circumnutation as common to all plants and the movements of climbing plants as a special modification of that general phenomenon.³ And this you have now convincingly, nay, superabundantly, proved to be the case.

I was much struck with the fact, that with you Maranta did not sleep for two nights after having its leaves violently shaken by wind; for here we have very cold nights only after storms from the west or southwest and it would be very strange, if the leaves of our numerous species of Marantaceae would be prevented, by these storms, to assume their usual nocturnal position, just when nocturnal radiation was most to be feared.⁴ It is rather strange also that Phaseolus vulgaris should not sleep during the early part of the summer, when the leaves are most likely to be injured during cold nights.—⁵ On the contrary it would not do any harm to many subtropical plants, that their leaves must be well illuminated during the day in order that they may assume at night a vertical position; for, in our climate at least, cold nights are always preceded by sunny days.

Of nearly allied plants sleeping very differently I can give you some more instances. In the genus Olyra (at least in the one species observed by me) the leaves bend down vertically at night; now in Endlicher’s Genera plantarum this genus immediately precedes Strephium, the leaves of which you saw rising vertically.⁶

In one of two species of Phyllanthus growing as weeds near my house, the leaves of the erect branches bend upwards at night, while in the second species, with horizontal branches, they sleep like those of Phyllanthus Niruri or of Cassia.⁷ In this second species the tips of the branches also are curled downwards at night, by which movement the youngest leaves are yet better protected. From their vertical nyctitropic position the leaves of this Phyllanthus might return to horizontality, traversing 90^o, in two ways, either to their own or to the opposite side of the branch; on the latter way no rotation would be required, while on the former each leaf must rotate on its own axis in order that its upper surface may be turned upwards. Thus the way to the wrong side appears to be even less troublesome. And indeed in some rare cases I have seen three, four or even almost all the leaves of one side of a branch horizontally expanded on the opposite side, with their upper surfaces closely appressed to the lower surfaces of the leaves of that side.

This Phyllanthus agrees with Cassia not only in its manner of sleeping, but also by its leaves being paraheliotropic.⁸ Like those of some Cassiæ its leaves take on almost perfectly vertical position, when at noon, on a summer day, the sun is nearly in the zenith; but I doubt, whether this paraheliotropism will be observable in England. To day, though continuing to be fully exposed to the sun, at 3 P.M. the leaves had already returned to a nearly horizontal position. As soon as there are ripe seeds, I will send you some; of our other species of Phyllanthus, I enclose a few seeds in this letter.⁹

In several species of Hedychium the lateral hal⁠⟨⁠ves⁠⟩⁠ of the leaves, when exposed to bright sunshine, bend downwards so that the lateral margins meet. It is curious, that a hybrid Hedychium in my garden shows scarcely any trace of this paraheliotropism, while both the parent species are very paraheliotropic.¹⁰

Might not the irregularity of the cotyledons of Citrus and of Pachira be attributed to the pression, which the several embryons enclosed in the same seed exert upon each other? I do not know Pachira aquatica, but in a species, of which I have a tree in my garden, all the seeds are polyembryonic, and so were also almost all the seeds of Citrus, which I examined. With Coffea arabica also seeds including two embryons, are not very rare; but I have not yet observed, whether in this case the cotyledons be inequal.¹¹

I repeated to day Duval-Jouve’s measurements on Bryophyllum calycinum; but mine did not agree with his; they are as follows.¹²

Distance between the tips of the upper pairs of leaves.

Jauary 9. 1881. 8 A.M. 1 P.M. 6 P.M.

First plant: 54 mm. 43 mm. 36 mm.

2^d – : 28 – 25 – 23.–

3^d – : 28.– 27.– 27.–

4^th – : 51.– 46.– 39.–

5^th – : 61.– 52.– 45.–

222 193 170

Recently my attention has been called by D^r Paul Mayer to an extremely interesting subject, viz. the fertilisation of figs by various hymenoptera. D^r Paul Mayer is now investigating with Prof. Solms-Laubach the “caprifrication” of figs and they have found a great many quite novel and unexpected facts, which will probably be published in the course of this year.¹³ D^r Mayer bade me to examine for him our wild figs and I have been able to confirm most of the observations, made in Italy.¹⁴ Our figs appear to possess even a richer fauna of peculiar hymenopterous insects; you may meet with five or six different species in the figs of a single tree. I must of course refrain from communicating to you P. Mayer’s interesting discoveries; but I may at least give you a rough sketch of some of the odd fellows to be found in our Figs.

From what I know of it, I think, D^r Mayer’s paper will be one of the most interesting contributions to entomology ever published, and Prof. Solms-Laubach’s botanical researches on the figs will probably be equally important.¹⁵

Repeating my cordial thanks and wishing that the new year may be a very happy one for you and your family I am, dear Sir, with the highest respect | Yours very faithfully | Fritz Müller.