Caseknife, introduced before 1820
Caseknife pod. Shaped a bit like a caseknife, presumably.
I just had a comment asking what had become of my Spagna Bianco, so here it is. It does appear to be botanically a runner bean but instead of the characteristic long thin runner pods it has ... er ... these. There are only two or three beans per pod by the look of it but they will be huge, round and plump like butterbeans.
Coco Bicolour, an old climber of French origin
Nun's Belly Button, a very old dwarf variety with several variants
Brighstone, from the Isle of Wight but of uncertain origin. Lovely purple flowers.
And after green beans you get other colours. This is Dog Bean.
I noticed some dark beans among my harvest of Mrs Fortune's last year which were almost totally purple instead of the usual tan with purple whorls. It was only three beans in the whole crop. I planted them separately to see whether they look different from the usual plants. And they do! They have more purple on them, the flowers are darker pink, and the pods develop a much deeper blue mottling. I don't think they've crossed with anything, I think it's more likely to be a spontaneous mutation or a hidden gene expressing itself. I will watch them with interest.