To Asa Gray   7 December 1870

My dear Gray

I have been very glad to receive yr letter this mg—¹ I have for some time been wishing to write to you, but have been half worked to death in correcting my uncouth English for my new book—² I have been glad to hear of yr cases appearing like incipient dimorphism. I believe that they are due to mere variability, & have no significance. I found a good instance in Nolana prostrata, & experimented on it, but the forms did not differ in fertility.³ So it was with Amsinckia of which you told me.⁴ I have long thought that such variations afforded the basis for the development of dimorphism. I was not aware of such cases in Phlox, but have often admired the arrangement of the anthers, causing them to be all raked by an inserted proboscis. I am glad also to hear of your curious case of variability in ovules &c.

I said that I had been wishing to write to you, & this was about yr Drosera, which after many fluctuations between life & death, at last made a shoot, which I c^d observe.⁵ The case is rather interesting; but I must first remind you that the filament of Dionæa is not sensitive to very light prolonged pressure, or to nitrogenous matter, but is exquisitely sensitive to the slightest touch. In our Droseræ the filaments are not sensitive to a slight touch, but are sensitive to prolonged pressure from the smallest object of any nature; they are also sensitive to solid or fluid nitrogenous matter. Now in y^r Drosera the filaments are not sensitive to a rough touch or to any pressure from non-nitrogenous matter, but are sensitive to solid or fluid nitrogenous matter. Is it not curious that there sh^d be such diversified sensitiveness in allied plants?⁶

I rec^d a very obliging letter from Mr Morgan, but did not see him, as I think he said he was going to start at once for the continent.⁷ I am sorry to hear rather a poor account of M^rs Gray to whom my wife I both beg to be very kindly remembered—⁸

My dear Gray | Yours affectionately | Ch Darwin