To Friedrich Hildebrand   9 February 1872

My dear Sir

Owing to other occupations I was able to read only yesterday yr paper on the Dispersal of the seeds of Compositæ. Some of the facts which you mention are extremely interesting.¹

I write now to suggest, as worthy of yr examination, the curious adhesive filaments of mucus emitted by the Achenia of many Compositae, of which no doubt you are aware. My attention was first called to the subject by the Achenia of an Australian Pumilio, (P. argyrolepis) which I briefly described in the Gardener’s Chronicle 1861. p. 5.²

As the threads of mucus dry & contract they draw the seeds up into a vertical position on the ground. It subsequently occurred to me that if these seeds were to fall on the wet hairs of any quadruped they w^d adhere firmly & might be carried to any distance. I was informed that Decaisne has written a paper on these adhesive threads.³ What is the meaning of the mucus so copiously emitted from the moistened seeds of Iberis & of, at least, some species of Linum?⁴ Does the mucus serve as a protection against their being devoured, or as a means of attachment?⁵

I have been prevented reading y^r paper sooner by attempting to read D^r Askenasy’s pamphlet;⁶ but the German is too difficult for me to make it all out.

He seems to follow Nägeli completely.⁷ I cannot but think that both much under-rate the utility of various parts of plants; and that they greatly under-rate the unknown laws of correlated growth, which leads to all sorts of modifications, when some one structure, or the whole plant, is modified for some particular object.

With sincere esteem believe me | my dear Sir | yours very faithfully | Charles Darwin