My dear F.

I begin to think that I shall prove that tip of radicle is its brain, as far as geotropism is concerned.—² I touched 4 tips with lunar caustic³ so as blacken only for $\frac{1}{2}$ to $\frac{2}{3}$ of m.m.— They grew in length during 24 h^rs 9 mm.. Now only 1 of the 4 became at all curved in the 24 h.— There were 4 other radicles in your jar, to which nothing had been done, & of these 3 after 24^hrs. pointed vertically downwards & one for some unknown reason was not acted on.— I showed George⁴ the jar & the contrast between the 4 which had been touched with L. Caustic & 4 which had not been touched, he thought most striking.

C. D.

I must try & retry many more radicles.—