Chapter 373

I have been very glad to receive your letter this morning. 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. (705/1. "Descent of Man.") I have been glad to hear of your cases appearing like incipient dimorphism. I believe that they are due to mere variability, and have no significance. I found a good instance in Nolana prostrata, and experimented on it, but the forms did not differ in fertility. So it was with Amsinckia, of which you told me. 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, etc.

I said that I had been wishing to write to you, and this was about your Drosera, which after many fluctuations between life and death, at last made a shoot which I could observe. The case is rather interesting; but I must first remind you that the filament of Dionoea is not sensitive to very light prolonged pressure, or to nitrogenous matter, but is exquisitely sensitive to the slightest touch. (705/2. In another connection the following reference to Dionoea is of some interest: "I am sure I never heard of Curtis's observations on Dionoea, nor have I met with anything more than general statements about this plant or about Nepenthes catching insects." (From a letter to Sir J.D. Hooker, July 12th, 1860.)) In our Drosera 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 your 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. (705/3. Drosera filiformis: see "Insectivorous Plants," page 281. The above account does not entirely agree with Darwin's published statement. The filaments moved when bits of cork or cinder were placed on them; they did not, however, respond to repeated touches with a needle, thus behaving differently from D. rotundifolia. It should be remembered that the last-named species is somewhat variable in reacting to repeated touches.) Is it not curious that there should be such diversified sensitiveness in allied plants?

I received 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. I am sorry to hear rather a poor account of Mrs. Gray, to whom my wife and I both beg to be very kindly remembered.