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