My dear Frank

If you did not dislike the job, I think it w^d. be a very good thing for you to review Wiesner. But you w^d. have to read his book very carefully & consult his greater work on Heliotropism, which I think we have.² I have now read $\frac{3}{4}$ of his book. It is a great comfort that he has repeated almost all our experiments & finds our statements correct, but it is almost laughable how different an interpretation he puts on every single case. Without intending it he is unfair in some cases, by ignoring many experiments & selecting only certain ones from which to deduce his results. This is conspicuously the case with respect to the sensitiveness of the tip to contact, which he says he has repeated 100 times & always with our result.³ But his explanation seems to me ludicrous, & this is due to his ignoring all my many trials with gum water & with bits of card on opposite sides. You will be enabled well to discuss diaheliotropism; his explanation of which, as far as I can understand it, seems to me ludicrous.⁴

His book seems to me really a model of the spirit in which everyone ought to write controversially.—

I give up the ghost about cutting off tips of radicles; but it is a wonderful fact that slight relaxation of power of growth sh^d entirely check geotropism. If you can see young & vigorously growing fir-trees—measure whether upper lateral horizontally growing shoots are ever as long as the leader.— I will explain why this is important.⁵

I shall be able to point out various points in which I differ from him; but you will of course have to judge for yourself entirely so as to write conscientiously, if you agree to review the book.—

Yours affec | C. Darwin

I wonder whether he had previously come to the conclusion that pressure & extension plays so important a part in apparently simple heliotropic curvatures, or whether he was led to this conclusion by our book.⁶

I forgot to thank about Pinguicola— experiment quite failed⁷