Brno, 3 July 1856

Brno, 3 July 1856

Dear Nägeli,

The bed of peas along the south wall of the monastery garden has given me what I did not expect. I counted 253 plants from the cross of the tall and the short, and every one came up tall. Not a single dwarf among them. Then I let those self-fertilise, and this year the second generation has come in at 787 tall and 277 short. That is 2.84 to 1. I have run the same cross with the round and the angular seed, with the yellow and the green cotyledon, and the ratio keeps returning to something near three to one. The short form does not vanish in the first generation. It hides, and reappears in the second in fixed proportion. This is not blending. If the characters blended, the dwarf would have diluted into the tall and never returned. Something discrete passes from parent to offspring, one factor from each side, and the recessive factor is not lost, only masked.

The n is adequate. I have not trusted a ratio below several hundred plants, and where the count was small I have said so and waited for the next season. Seven hundred and eighty-seven against two hundred and seventy-seven is not a small sample. It is a population, and the population has structure.

I am not writing to ask you to accept the interpretation of the factors. That can wait. I am writing because I have forty reprints of the paper on plant hybrids ready to send, and I am sending you one, and I already know what will happen to the other thirty-nine. They will sit on desks in Berlin and Vienna and Kew, and no one will open them, because the question I am asking is not the question anyone is asking this year. The result is correct. The routing is the problem. I have decided to run the cross on a fourth character, the pod form, through the next two seasons, and to publish the combined counts as a single table rather than in pieces, so that the ratio stands or falls on the whole population and not on any one year’s bed.