Pairing in Mendel's Theory

Abstract

IN his paper 'Mendel no Mendelian' published in 1979, Robert Olby discusses Mendel's experimental results with Phaseolus and his interpretations of them. Olby concludes that Mendel's 'treatment of flower colour in Phaseolus suggests that he was not even thinking of the pair of mutually excluding factors or the Allel (Bateson's Allelomorph). Later Olby discusses the 'Mendel Notiziblatt', a page of manuscript in Mendel's handwriting. He concludes: 'From this we learn that Mendel could conceive of three contrasted characters which can exist together in the F1 hybrid, but which are mutually exclusive in the germ cells.'2 What Olby means is that Mendel's conception was equivalent to supposing that alleles could be grouped into threes instead of being paired as in current theory. Hence, Olby endorses the view expressed by Heimans, explicity rejecting the importance of the notion of pairing in Mendel's thought.3 This is the issue to which attention is directed here. Towards the end of the Pisum paper, Mendel discusses his results obtained from experiments with Phaseolus. Although '[an] experiment with Phaseolus vulgaris and Phaseolus nanus L.' gave results similar to those obtained with Pisum, when Mendel crossed 'two very different Phaseolus species' his results were 'only partly successful.'4 Mendel maintains that: