My dear Hooker

What two very interesting & useful letters you have sent me.² You rather astound me with respect to value of grounds of generalisation in the morphology of plants.³ It reminds me that years ago I sent you a grass to name & your answer was “it is certainly Festuca — (so & so) but it agrees as badly with the description as most plants do.”!⁴ I have often laughed over this answer of a great Botanist.— All that which you say about “chorisis” is as new to me as the term itself:⁵ I will be cautious; the notion seemed to me monstrous, & I should still think it so, unless in an allied plant I can show gradation towards it; & then surely you would admit that it was at least possible.— But I have not yet looked at Bonatea, & the longer it soaks in Spirits the better.—⁶

Lindley, from whom I asked for an orchid with simple Labellum has most kindly sent me a lot of what he marks “rare” & “rarissimo” of peloric orchids &c; but as they are dried, I know not whether they will be of use.⁷ He has been most kind & has suggested my writing to Lady D. Nevill who has responded in wonderfully kind manner & has sent a lot of treasures.⁸ But I must stop, otherwise by Jove I shall be transformed into a Botanist. I wish I had been one: this morphology is surprisingly interesting. Looking to your note, I may add that certainly the 15 alternating bundles of spiral vessels (mingled with odd bead-like vessels in some cases) are present in many Orchid; the inner whorl of anther-ducts are oftenest aborted.— I must keep clear of Apostasia, though I have cast many a longing look at it in Bauer.—⁹

What a very interesting case that of the Crucifer with many stamens & its relation to Papavers!—

Your note about St. Thomas is wonderfully curious: the mammals in Fernando Po show it was anciently united to mainland: but as far as I can remember I concluded on investigation that the mammals in St. Thomas were all introduced, & that the isl^d. had always been an island. Do you not think that this will bear on non-migration during glacial period. Is there not great dearth of temperate forms on Teneriffe?¹⁰

Pray thank heartily that living index, Oliver, for telling me of French Book, which is ordered.—¹¹

I hope I may be well enough to read my own paper on Thursday, but I have been very seedy lately:¹² I see that there is paper at Royal on same night at Royal, which will more concern you on fossil plants of Bovey;¹³ so that I suppose I shall not have you; but you must read my paper when published, as I shall very much like to hear what you think. It seems to me a large field for experiment.— I am now trying one on Heterocentron roseum a Melastomatous plant with 2 sorts of anthers.¹⁴ I shall make use of my Orchid little volume in illustrating modification-of-species-doctrine; but I keep very very doubtful whether I am not doing a foolish action in publishing. How I wish you would keep to your old intention & write a book on Plants.¹⁵

Adios my dear old friend | C. Darwin

It strikes me as a fundamental point in value of Homologies of Ducts, in what course they are developed & I cannot find out this: when a petal is first formed, is the duct in it a prolongation upwards from a bundle below, or downwards from the petal to join a previously existing duct.— If the latter one can see how the ducts might go astray.—

(By odd chance I have just stumbled on dispute on this point in Bull. Soc. Bot. & I see both opposite views stoutly maintained.)¹⁶