Many of your criticisms on my views are the best which I have met with, but I could answer some, at least to my own satisfaction; and I regret extremely that I had not read your pamphlet before printing my new edition. On one or two points, I think, you have a little misunderstood me, though I dare say I have not been cautious in expressing myself. The remark which has struck me most, is that on the position of the leaves not having been acquired through natural selection, from not being of any special importance to the plant. I well remember being formerly troubled by an analogous difficulty, namely, the position of the ovules, their anatropous condition, etc. It was owing to forgetfulness that I did not notice this difficulty in the 'Origin.' (Nageli's Essay is noticed in the 5th edition.) Although I can offer no explanation of such facts, and only hope to see that they may be explained, yet I hardly see how they support the doctrine of some law of necessary development, for it is not clear to me that a plant, with its leaves placed at some particular angle, or with its ovules in some particular position, thus stands higher than another plant. But I must apologise for troubling you with these remarks.
As I much wish to possess your photograph, I take the liberty of enclosing my own, and with sincere respect I remain, dear Sir,
Yours faithfully, CH. DARWIN.
[I give a few extracts from letters of various dates showing my father's interest, alluded to in the last letter, in the problem of the arrangement of the leaves on the stems of plants. It may be added that Professor Schwendener of Berlin has successfully attacked the question in his 'Mechanische Theorie der Blattstellungen,' 1878.
TO DR. FALCONER. August 26 [1863].
"Do you remember telling me that I ought to study Phyllotaxy? Well I have often wished you at the bottom of the sea; for I could not resist, and I muddled my brains with diagrams, etc., and specimens, and made out, as might have been expected, nothing. Those angles are a most wonderful problem and I wish I could see some one give a rational explanation of them."
TO DR. ASA GRAY. May 11 [1861].
"If you wish to save me from a miserable death, do tell me why the angles 1/2, 1/3, 2/5, 3/8, etc, series occur, and no other angles. It is enough to drive the quietest man mad. Did you and some mathematician (Probably my father was thinking of Chauncey Wright's work on Phyllotaxy, in Gould's 'Astronomical Journal,' No.99, 1856, and in the 'Mathematical Monthly,' 1859. These papers are mentioned in the "Letters of Chauncey Wright.' Mr. Wright corresponded with my father on the subject.) publish some paper on the subject? Hooker says you did; where is it?
TO DR. ASA GRAY. [May 31, 1863?].
"I have been looking at Nageli's work on this subject, and am astonished to see that the angle is not always the same in young shoots when the lea-buds are first distinguishable, as in full-grown branches. This shows, I think, that there must be some potent cause for those angles which do occur: I dare say there is some explanation as simple as that for the angles of the Bees-cells."