To S. H. Vines   1 November 1881

My dear M^r Vines

As I know how busy you are it is a great shame to trouble you.— But you are so rich in chemical knowledge about plants, & I am so poor, that I appeal to your charity as a pauper.— My question is, do you know of any solid substance in the cells of plants which glycerine & water dissolves? But you will understand my perplexity better, if I give you the facts.— I mentioned to you that if a plant of Euphorbia peplus is gently dug up & the roots placed for a short time in a weak solution (1 to 10,000 of water suffices in 24 hr.) of Carbonate of Ammonia, the (generally) alternate longitudinal rows of cells in every rootlet, from the root-cap up to the very top of the root, (but not as far as I have yet seen in the green stem) become filled with translucent, brownish grains of matter.¹ These rounded grains often cohere & even become confluent. Pure Phosphate & Nitrate of Ammonia produce (though more slowly) the same effect, as does pure Carbonate of Soda.²

Now if slices of root under a cover-glass are irrigated with glycerine & water, every one of the innumerable grains in the cells disappear after some hours.³ What am I to think of this?

My son Frank, when he was at home, maintained that these cells must be modified milk or laticiferous tubes.⁴ But then, as far as I have yet seen, no such process of aggregation takes place in the stem.— Owing to my confounded ignorance I cannot find the milk tubes in the roots.—

Forgive me for bothering you to such an extent; but I must mention that if the roots are dipped in boiling water, there is no deposition of matter, & Carbonate of Ammonia afterwards produces no effect. I sh^d. state that I now find that the granular matter is formed in the cells immediately beneath the thin epidermis, & in a few other cells near the vascular tissue. If the granules consisted of living protoplasm, (but I can see no trace of movement in them) then I sh^d. infer that the glycerine killed them & aggregation ceased with the diffusion of invisibly minute particles; for I have seen an analogous phenomenon in Drosera.⁵

If you can aid me, pray do so, & anyhow forgive me.

Yours very sincerely | Ch. Darwin

It has just occurred to me that I may have put the slices of the stem of Euphorbia after immersion in C. of Ammonia into glycerine & water, for the sake of transparency, & then if granules were formed they would have disappeared.—