My dear Darwin,

I go to town on Tuesday & on to Cheltenham on Thursday—¹ Are you to be there? L. Jenyns writes me word he wants to get up a discussion about the limitation of species—² He means to attack the subject thro’ Ornithology. I have a case or two this year among plants— ³

I have clearly reduced Centaurea nigrescens or decipiens (of Bab. ⁴ ) to C. nigra, after about 4 years culture— I think I told you I have had a small bed of Ægilops squarrosa self sown for the last 3 or 4 years— This year one plant in the very midst of the patch assumed the triticoidal character, which has been noticed in 2 other species—⁵ I have carefully netted it—& watched it but from its appearance I begin to fear it will not ripen any seed. I had fancied it to be a clear example of Ægilops passing to wheat—& certainly it is a most remarkable plant— It may however be a hybrid between the Ægilops & some revet wheat (?)— It is upright, & the ear has long straight awns & is quite downy. Would you like some seeds of the Ægilops now ripe?⁶ I have manured a piece of the border next the patch, & mean to extend my experiment next year over it— You have not told me yet what seeds you would like us to get for you— We have been in a greater