Dear M^r Darwin

The plants were sent to you yesterday and I hope have reached you in good condition.¹

With regard to Mimosa Sensitiva, I see that Bentham in his monograph of the Mimoseæ. Trans, Linn. Soc. XXX, p. 390 considers that the Linnean species comprised four or five nearly allied forms that are now considered distinct.²

You have I think our plant of Mimosa albida Humb. & Bonpl. of which Bentham remarks “This is the species or variety which most commonly represents the M. sensitiva of our gardens”.³ It is also no doubt the plant which has always been intended in horticultural literature as M. Sensitiva. So I think you may safely take it as the plant which physiologists have had in their minds and laboratories. The true plant is practically the same but the leaflets are more acute and the whole plant is hairy or villous rather than cano-pubescent⁴   They are in fact only geographical races. M. sensitiva Eastern, & M. albida western. However I have written out to Brazil for seed

Yours very truly | W. T. Thiselton Dyer