I was struck with your remark about the Compositae, etc. I do not see that it bears much against me, and whether it does or not is of course of not the slightest importance. Although I fully agree that no definition can be drawn between monstrosities and slight variations (such as my theory requires), yet I suspect there is some distinction. Some facts lead me to think that monstrosities supervene generally at an early age; and after attending to the subject I have great doubts whether species in a state of nature ever become modified by such sudden jumps as would result from the Natural Selection of monstrosities. You cannot do me a greater service than by pointing out errors. I sincerely hope that your work on monstrosities (99/1. "Vegetable Teratology," London, 1869 (Ray Soc.).) will soon appear, for I am sure it will be highly instructive. Now for your notes, for which let me again thank you. 1. Your conclusion about parts developed (99/2. See "Origin of Species," Edition I., page 153, on the variability of parts "developed in an extraordinary manner in any one species, compared with the other species of the same genus." See "Life and Letters," II., pages 97, 98, also Letter 33.) not being extra variable agrees with Hooker's. You will see that I have stated that the rule apparently does not hold with plants, though it ought, if true, to hold good with them. 2. I cannot now remember in what work I saw the statement about Peloria affecting the axis, but I know it was one which I thought might be trusted. I consulted also Dr. Falconer, and I think that he agreed to the truth of it; but I cannot now tell where to look for my notes. I had been much struck with finding a Laburnum tree with the terminal flowers alone in each raceme peloric, though not perfectly regular. The Pelargonium case in the "Origin" seems to point in the same direction. (99/3. "Origin of Species," Edition I., page 145.) 3. Thanks for the correction about furze: I found the seedlings just sprouting, and was so much surprised and their appearance that I sent them to Hooker; but I never plainly asked myself whether they were cotyledons or first leaves. (99/4. The trifoliate leaves of furze seedlings are not cotyledons, but early leaves: see Lubbock's "Seedlings," I., page 410.) 4. That is a curious fact about the seeds of the furze, the more curious as I found with Leguminosae that immersion in plain cold water for a very few days killed some kinds. If at any time anything should occur to you illustrating or opposing my notions, and you have leisure to inform me, I should be truly grateful, for I can plainly see that you have wealth of knowledge. With respect to advancement or retrogression in organisation in monstrosities of the Compositae, etc., do you not find it very difficult to define which is which? Anyhow, most botanists seem to differ as widely as possible on this head. LETTER 100. TO J.S. HENSLOW. Down, May 8th [1860].