wishes for the success of your Travels.

LETTER 135. TO J.D. HOOKER. Down, March 18th [1862].

Your letter discusses lots of interesting subjects, and I am very glad
you have sent for your letter to Bates. (135/1. Published in Mr. Clodd's
memoir of Bates in the "Naturalist on the Amazons," 1892, page l.) What
do you mean by "individual plants"? (135/2. In a letter to Mr. Darwin
dated March 17th, 1862, Sir J.D. Hooker had discussed a supposed
difference between animals and plants, "inasmuch as the individual
animal is certainly changed materially by external conditions, the
latter (I think) never, except in such a coarse way as stunting or
enlarging--e.g. no increase of cold on the spot, or change of individual
plant from hot to cold, will induce said individual plant to get more
woolly covering; but I suppose a series of cold seasons would bring
about such a change in an individual quadruped, just as rowing will
harden hands, etc.") I fancied a bud lived only a year, and you could
hardly expect any change in that time; but if you call a tree or plant
an individual, you have sporting buds. Perhaps you mean that the
whole tree does not change. Tulips, in "breaking," change. Fruit seems
certainly affected by the stock. I think I have (135/3. See note, Letter
16.) got cases of slight change in alpine plants transplanted. All these
subjects have rather gone out of my head owing to orchids, but I shall
soon have to enter on them in earnest when I come again to my volume on
variation under domestication.

...In the lifetime of an animal you would, I think, find it very
difficult to show effects of external condition on animals more than
shade and light, good and bad soil, produce on a plant.

You speak of "an inherent tendency to vary wholly independent of
physical conditions"! This is a very simple way of putting the case (as
Dr. Prosper Lucas also puts it) (135/4. Prosper Lucas, the author of
"Traite philosophique et physiologique de l'heredite naturelle dans
les etats de sante et de maladie du systeme nerveux": 2 volumes,
Paris, 1847-50.): but two great classes of facts make me think that all
variability is due to change in the conditions of life: firstly, that
there is more variability and more monstrosities (and these graduate
into each other) under unnatural domestic conditions than under nature;
and, secondly, that changed conditions affect in an especial manner the
reproductive organs--those organs which are to p