My dear Dyer

I have not troubled you or Hooker for a long time, as I have been on a holiday & writing life of D^r. Darwin, which is abominable work as one does not know what to believe or what is worth telling.¹

I now want you to get M^r. Lynch or some one to look out for any plant with aerial roots which are either heliotropic or apoheliotropic; but not a precious plant, as I shall be in constant fear with it & must injure many of the roots.² If I knew what to order I would buy any that would serve. I am very anxious to experimentise on such roots with reference to light, because I have proved, wonderful as the fact is, that the apex of a root acts functionally like a brain & commands the nature of the flexure in the upper part. This applies to touch, some other stimulants & geotropism; & I now want to know about light. It is pretty to see the effect of a touch of lunar caustic on extreme tip of radicle, how it annuls the effect of geotropism, though the radicle goes on growing quite well.³

If you are able to send me any plants, I must be told what temperature to keep them in. I believe that the roots of some Aroids are affected by light.⁴ Help me if you can, but I am not very sanguine.—

I hope that you are all well & flourishing at Kew.

Ever yours sincerely | Ch. Darwin

Frank seems happy & working hard at Würzburg.—⁵

Do you remember getting me seed of Drosophyllum from Portugal; alas not one germinated. If you have plants at Kew & they sh^d. flower could you get me some fresh seed.—⁶