Dear Sir!

I am very much obliged to you for your great kindness of sending me your Work on the Power of Movement in plants, which I have read with the greatest interest.¹ I was much pleased to learn by your experiments that circumnutation is a general phenomenon in all growing plants, and that it is the basis of most of the other movements of vegetable organs. The little oscillations you describe in these circumnutating movements seem to remind of the “stossweise Aenderungen des Wachsthums” of Sachs.² For if it is allowed to assume that these little “shocks” do not occur at the same time on all sides of the growing organ, the result must be a similar movement as those described by you. I was especially interested by your experiments on the movements and the curious sensitiveness of the roots and plumules of young seedling-plants, which I hope to repeat as soon as I shall have an occasion, for I desire very much to observe myself these interesting and unexpected phenomena.³ I always remember the great pleasure, I had in repeating the experiments, described in your work on Insectivorous plants, with all those species, which I could procure either in botanical gardens or on excursions.⁴ By so doing I not only obtained a better knowledge of the subject, but often had the opportunity of showing these phenomena to others. And now I always cultivate some Utricularia, Drosera and Pinguicula, so as to be able to show their insectivorous habits to my students every year.

Your considerations on the embryology of leaves remembered me the curious case afforded by the young plants of Sium latifolium, which have their leaves divided in a much higher degree than the pinnated leaves of the older plants, and so show their descent from an Umbelliferous type with highly divided leaves.⁵ So your experiments and remarks on the danger, occasioned by the radiation during cold nights, suggested to me, that perhaps the hairs of plants might in many cases have been acquired for the same purpose as the sleeping movements, and that this supposition would account for the curious instance that so many leaves are covered with hairs when young, and lose them when growing older.⁶

In your Work you often speak of my papers on the same subject, and I am much indebted to you for your very kind judgment on them, which will be a stimulus to me in endeavouring to contribute my part to the advancement of science.⁷

With many thanks | Yours sincerely. | Hugo de Vries.