My dear Hooker.

Thanks for note.¹ It seems that I cannot exhaust your goodnature. I have had the hardest day’s work at Catasetum & buds of Mormodes, & believe I understand at last mechanism of movements & function.— Catasetum is beautiful case of slight modification of structure leading to new function. I never was more interested in any subject in my life, than in this of Orchids.— I owe very much to you.—

Now for points to attend to.—

Does viscid surface of rostellum (or gland) in Cycnoches or Mormodes project beyond stigmatic cavity; or does it not lie (as in bud & as in mature Catasetum) within roof of stigmatic cavity. But you must not touch, you must judge by looks.—

2^d. First touch base of Column; then touch basal edge of a curtain which depends (I suppose) in front of stigmatic cavity; then touch round smooth surface in middle over stigmatic cavity; & lastly touch either of two slight prominent knobs on side of stigmatic cavity: This latter point, I expect, will be sensitive & will cause pollinia to be ejected with force, gland foremost.— I judge from Catasetum: Which is the sensitive point I want most to know. Touch lightly with needle or bristle; & secondly whether gland-end is not projected foremost?— I cannot believe that pollinia would hit own stigma???   I can imagine that it may fertilise itself & this would be most important point for me.

I have written to M^r Veitch begging him to let me buy flowers, if any more open & I will send Parslow up to carry them down in hand.² Would it not save you trouble if I were to do same i.e. send servant to Kew? that is if you can spare me a flower or two.— Perhaps this would be best for me.—

If any flower of great tribe of Arethuseæ sh^d. open, please remember how much I wish to see one.—³ Hearty thanks for information about vascular vessels;⁴ I shall do a bit more work at them.

If it does not trouble Oliver will you ask him to look once again within sack of Stanhopea; for it is not very likely that there sh^d. be nectar till after flower has opened for some days & been well shone on.⁵

Your affect. | C. Darwin

See how pretty it is; an insect could not touch sticky gland of Catasetum, from its sticky surface lying close to roof of stigmatic chamber; consequently it is projected, sticky end first, with wonderful force, right on head or shoulders of an insect crawling on the Labellum.—