My dear M^r. Vines,

I hope that you will excuse me troubling you once again about the roots of Euphorbia peplus.¹ I can see my way a little & but a very little way clearer, for by examining the radicles of germinating seeds I have learnt the appearance of the milk-tubes, & beautiful objects they are. Now in the rootlets of mature plants of Euphorbia peplus these tubes are absent, & I remember that De Bary says that he could not succeed in seeing them in the finer roots of Euphorbia, but I must hunt up the passage.² The usually alternate rows of cells with brown granular matter near the surface & those in the Endoderm, I imagine replace by their contents the contents of the true milk-tubes; though I must own that the contents are not chemically the same, as Caustic potash does not act on the aggregated granular masses in the milk-tubes, whereas it causes the disappearance of the granular matter which is precipitated by C. of Ammonia & other salts, in the cells.— If you ever look at the roots of E. peplus, I sh^d. very much like to hear what you think about them. With Euphorbia myrsinites,³ there are no regular rows of cells with granular matter after Ammonia, & only here & there one, or two or three cells in a row with the granular matter; & in the mature rootlets of this species only a few milk-tubes are present; but I must look to other species of Euphorbia.—

I remain | Yours very sincerely | Ch. Darwin

P.S. | I remember telling you about Wiesners vivisection of me, & I was pleased yesterday by receiving a letter from Pfeffer, who has been retrying some of my experiments & differs from Wiesner.⁴ But Pfeffer differs vehemently on other points from me; so I am in fine hot water.