My dear M^r. Bentham

I venture a beg a favour of you. I have rather a wild bit of speculation afloat on the crossing of plants; & the Leguminosæ are my determined enemies, & worst of all are any forest-trees of this order.² Now the only book which I have as any sort of guide is Loudon Encyclop. of Plants;³ & as far as I can most imperfectly judge; the Leguminosæ in the two sub-orders Cæsalpinieæ & Mimoseæ are mostly Trees or bushes— is this so? But what concerns me most is to know whether there are many timber trees with papilionaceous flowers, ie with a keel enclosing the stamens & pistil, so as to shut them up as in a common Pea.— In Loudon to my joy the little woodcuts seem to show that the trees Dipterix, Parivoa & Erythrina have the stamens protruding, unlike common papilionaceous flowers:— on the other hand, to my sorrow the trees Dalbergia Pongamia, Pterocarpus, Butea & Piscidia have flowers shut up just like a Pea.— Do you know these trees, & is my inference right? And can you say, whether the papilionaceous division of the Leguminosæ have as many trees as the two other divisions; or (but this is a very loose question) as many trees as most orders which have any trees?

(I have forgotten Robinia, but this I can myself watch to see if the keel opens next summer.)

Will you humour me in giving me a little information on this head, which I am very curious about, though the notion which I am testing is very wild.— I ought to be ashamed of myself to ask you to take so much trouble, but a brief answer, if you will kindly give me one, will suffice.—

Pray believe me, | Your’s very sincerely | Ch. Darwin

P.S. | I have been comparing all the evidence which I can collect on the natural crossing of the varieties of cultivated Leguminosæ; & it is most conflicting; but preponderates against crossing ever taking place.⁴ Do you happen to know of any facts throwing light on this question?—

Are many of the Cæsalpinieæ polygamous like many of the Mimoseæ?