I am now working on the habits of worms, and it tires me much to change my subject; so I will lay on one side your letter and my notes, until I have a week's leisure, and will then see whether my facts bear on your views. I will then send a letter to "Nature" or to the Linn. Soc., with the extract of your letter (and this ought to appear in any case), with my own observations, if they appear worth publishing. The subject had gone out of my mind, but I now remember thinking that the imperfect action of the crimson stamens might throw light on hybridism. If this pollen is developed, according to your view, for the sake of attracting insects, it might act imperfectly, as well as if the stamens were becoming rudimentary. (629/2. As far as it is possible to understand the earlier letters it seems that the pollen of the shorter stamens, which are adapted for attracting insects, is the most effective.) I do not know whether I have made myself intelligible.

LETTER 630. TO W. THISELTON-DYER. Down, March 21st {1881}.

I have had a letter from Fritz Muller suggesting a novel and very curious explanation of certain plants producing two sets of anthers of different colour. This has set me on fire to renew the laborious experiments which I made on this subject, now 20 years ago. Now, will you be so kind as to turn in your much worked and much holding head, whether you can think of any plants, especially annuals, producing 2 such sets of anthers. I believe that this is the case with Clarkia elegans, and I have just written to Thompson for seeds. The Lythraceae must be excluded, as these are heterostyled.

I have got seeds from Dr. King of some Melastomaceae, and will write to Veitch to see if I can get the Melastomaceous genera Monochaetum and Heterocentron or some such name, on which I before experimented. Now, if you can aid me, I know that you will; but if you cannot, do not write and trouble yourself.

2.X.III. CORRESPONDENCE WITH JOHN SCOTT, 1862-1871.

"If he had leisure he would make a wonderful observer, to my judgment; I have come across no one like him."—Letter to J.D. Hooker, May 29th {1863}.

(631/1. The following group of letters to John Scott, of whom some account is given elsewhere (Volume I., Letters 150 and 151, and Index.) deal chiefly with experimental work in the fertilisation of flowers. In addition to their scientific importance, several of the letters are of special interest as illustrating the encouragement and friendly assistance which Darwin gave to his correspondent.)

LETTER 631. JOHN SCOTT TO CHARLES DARWIN. Edinburgh Botanic Gardens, November 11th, 1862.

I take the liberty of addressing you for the purpose of directing your attention to an error in one of your ingenious explanations of the structural adaptations of the Orchidaceae in your late work. This occurs in the genus Acropera, two species of which you assume to be unisexual, and so far as known represented by male individuals only. Theoretically you have no doubt assigned good grounds for this view; nevertheless, experimental observations that I am now making have already convinced me of its fallacy. And I thus hurriedly, and as you may think prematurely, direct your attention to it, before I have seen the final result of my own experiment, that you might have the longer time for reconsidering the structure of this genus for another edition of your interesting book, if indeed it be not already called for. I am furthermore induced to communicate the results of my yet imperfect experiments in the belief that the actuating principle of your late work is the elicitation of truth, and that you will gladly avail yourself of this even at the sacrifice of much ingenious theoretical argumentation.

Since I have had an opportunity of perusing your work on orchid fertilisation, my attention has been particularly directed to the curiously constructed floral organs of Acropera. I unfortunately have as yet had only a few flowers for experimental enquiry, otherwise my remarks might have been clearer and more satisfactory. Such as they are, however, I respectfully lay {them} before you, with a full assurance of their veracity, and I sincerely trust that as such you will receive them.