From J. D. Hooker [11 April 1857]1
I came down here on Thursday, when also my wife came from Brighton & yours from the North— the latter met on the Railway station. Mrs. D. seems well & strong, Etty is thin & pale but not looking worn or anxious, I do hope the change will do her good. they have taken lodgings, which look well, close by here & go in today.2
If you knew how grateful the turning from the drudgery of my “professional Botany” to your “philosophical Botany” was, you would not fear bothering me with questions— the truth in its positive nakedness is, that I really look for & count upon such questions, as the best means of keeping alive a due interest in these subjects. I indulge vague hopes of treating of them some day, but days & years fly over my head & all I do is done in correspondence to you, but for which I should soon loose sight of the whole matter.
Harveys observation on Fucus varying much & yet in same way under most different conditions goes with me for a great deal & I would endorse it.3 D. Don’s on Juncus bufonius in England & India I would not put in the same scale but is good By the oddest chance I was, on the day of the arrival of your letter, doing Indian Juncus bufonius, several hundred specimens from 8 or 10 different localities, from plains of Panjab to elev. 9000 feet in Sikkim. Now I find the best marked English varieties (& these are very wide) amongst the Indian ones, just as Don did, & as none of the conditions except that of Sikkim (which maybe compared rudely to W of Scotland) are at all like Britain, we may I suppose assume it to be a good case in point. The Polygala case is as good in its way, & you may add Anagallis arvensis which varies Red, blue & white in N. W India, as in England.
Cardamine hirsuta, presents in Fuegia & N. Zealand, most (if not all) its European phases, besides many more.
There are I think heaps such cases, they have so often struck me, that one of my sketched out methods of treating of the Indian plants common to W. Europe & India is by dividing them into diag 1. Identical unvarying species
2. Identical variable species
α variations equal & similar in both countries
β. variations unequal or dissimilar or bothramme Oxalis corniculata I believe to be as good a case, but it is as well to avoid a genus upon which Botanists are so notoriously divided in opinion
I am sorry that I cannot at all answer the Sonchus question; but as the wild Sonchus is not very common I suppose the introduced will soon be by far the most so.
The Taraxacum dens-Leonis must be a parallel case; as also Alsine media, & Cardamine hirsuta, though they have not yet forced themselves on the notice of Botanists.
I shall return to Kew on Monday & send you any further notices of plants varying simila〈r〉l〈y〉 under widely different conditions.
Ever Yrs | J D Hooker
JDH cites W. H. Harvey’s observations on Fucus and David Don’s on Juncus as examples of variations that are independent of climate. There are many such cases. Gives his working scheme for categorising variation.