My dear Darwin

The only drawback I have to the pleasure your xcellent letters afford me is, the thoughts that you may be kind enough to feel yourself in some measure obliged to answer my interminable yarns—though it may be long before you will allow yourself to think so.

Very many thanks for all the information you give me, if everyone who had information to give, was equally ready to impart, I think that science would advance too fast for me at least

I cannot call to remembrance any marked case of a genus having a set of var^ble. sp. in one area & better marked ones in another, but there are partial instances, & a good many—Rubi for instance in some countries as S. Am. & the E. Ind. are I believe more invariable than here, but I am not speaking on very good grounds as I have never xamined & there are few of them as you say— Vaccinia are certainly very bad in N. Am. but the much fewer Europ. sp. are good ones. Certainly Cape Ericeæ vary, but I am not prepared to say that the Europ. ones are very well behaved, but shall ask Mr Bentham. I have asked my father the question & as far as he can recollect he agrees with me, that the converse holds good to an alarming xtent. All the large mundane genera of Cruciferæ, Caryophylleæ, Ranunculus, Grasses, Cyperaceæ &c. are very bad every where. I am not however prepared to say that mundane genera vary in proportion to their size, as some solitary mundane genus of a single species will vary enough for a whole Nat. ord. On the other hand there a few mundane genera which are pretty good all over the world, thus Boott does not think Carex so bad.¹

With regard to Lycopodium the more I examine them the more thoroughly I am convinced of the identity of a few species all over the globe, & my Selago xample is only one of several parallel cases in the same genus. All that I can at present say is, that if (as I believe) Selago is a variety of varium, then that it is not so variable a plant in the N. temp. zone as in tropics or South, for if once it is conceded that it is said var. there is no saying where the variation is to stop, without it turns into itself again as I hope it will, through whatever changes it may go I care not.— I am preparing to write (commit myself) on the subject.

I should very much like to hear about this river that Humboldt mentions, I cannot think of any analogous case.— There is a V. D L. bird xcessively common on the E. side of the Derwent which has never been seen on the W. south of Rosneath (about 10 miles above Hobart. I can vouch for this as far as my xperience of a few days goes & many most intelligent persons have told me the same & who pointed the fact out to me: I have a note of it somewhere.

The gum trees are an instance of a very large genus confined within very narrow limits, being very variable, yet one most distinct species covers about 2 acres only on one side of narrow valley opposite Hobart, its limits are as marked as possible, no one has seen it elsewhere, nor are there scattered young trees about it, it occupyes the ground for a little space or nearly so, it is distinguishable $\frac{1}{2}$ mile off.— I believe parallel Australian cases are not rare in other constant genera, but not in so Protean a one as Eucalyptus

My name is down for the Athen. & has been I cannot tell how long, some 2 years I believe, but do not know, I xpect I have 2 more to wait at least xcept they will make a committee member of me as they did of D^r Graham & Richardson² & may of me if ever I attain their eminence, & am not black balled before. The expense of the Geolog. deters me, as I do not belong to the Royal yet, besides the almost impracticability of my attending the meetings: the Linnæan I am more in duty bound to meet with but can hardly ever go.³

I should like very much to steal a holiday about the beginning of Dec^r. & accept your & Mrs Darwin’s most kind offer, but will you not (my father bids me say) come here one night of 19, 20, or 21^st.; just one, I will meet you in Town; a $\frac{1}{4}$–5 Omnibus is plenty time for our 6 dinner we shall be alone & I will promise you quiet & may go as early as you like next morning, I want to be in town on one of those days, it is immaterial which. My mother is copying out the 1^st. century of Gal. Isd. plants for L. Soc.⁴ I did not tell you that I had to withhold it, from Henslowes sending me a supplement, which my book prevented my working up. ⁵

Ever most truly yours, J D Hooker.