My dear Romanes,—I have read your two articles in 'Nature,' and nothing can be clearer or more interesting, though I had gathered your conclusions clearly from your other papers. It seems to me that unless you can show that your muslin (in your simile) is rather coarse, the transmission may be considered as passing in any direction from cell or unit of structure to cell or unit; and in this case the transmission would be as in Dionæa, but more easily effected in certain lines or directions than in others. It is splendid work, and I hope you are getting on well in all respects. The Mr. Lawless to whom you refer is the Hon. Miss Lawless, as I know, for she sent me a very good manuscript about the fertilisation of plants, which I have recommended her to send to 'Nature.'
As for myself, Frank and I have been working like slaves on the bloom on plants, with very poor success; as usual, almost everything goes differently from what I had anticipated. But I have been absolutely delighted at two things: Cohn, of Breslau, has seen all the phenomena described by Frank in Dipsacus, and thinks it a very remarkable discovery, and is going to work with all reagents on the filaments as Frank did, but no doubt he will know much better how to do it. He will not pronounce whether the filaments are some colloid substance or living protoplasm; I think he rather leans to latter, and he quite sees that Frank does not pronounce dogmatically on the question.
The second point which delighted me, seeing that half of the botanists throughout Europe have published that the digestion of meat by plants is of no use to them—(a mere pathological phenomenon as one man says!)—is that Frank has been feeding under exactly similar conditions a large number of plants of Drosera, and the effect is wonderful. On the fed side the leaves are much larger, differently coloured, and more numerous—flower stalks taller and more numerous, and, I believe, far more seed-capsules, but these not yet counted. It is particularly interesting that the leaves fed on meat contain very many more starch granules (no doubt owing to more protoplasm being first formed), so that sections stained with iodine of fed and unfed leaves are to the naked eye of very different colour.
There, I have boasted to my heart's content; and do you do the same, and tell me what you have been doing.
Yours very sincerely,
Ch. Darwin.
From G. J. Romanes.
Dunskaith, Ross-shire: August 11, 1877.
I was very pleased to get your long and genial letter, which I will answer seriatim.
The 'muslin' in the hypothetical plexus seems to be very coarse in some specimens and finer in others—the young and active individuals enduring severer forms of section than the old. And in exploring by graduated stimuli, areas of different degrees of excitability may be mapped out, and these areas are pretty large, averaging about the size of one's finger-nails. I am rather inclined to think that these areas are determined by the course of well-differentiated nerve-tracts, while the less-differentiated ones are probably more like muslin in their mesh. But the only reason why I resort to the supposition of nerve-tracts at all is because of the sudden blocking of contractile waves by section, and the fact that stimulus (tentacular) waves very often continue to pass after the contractile ones have been thus blocked.