Bei Pisum treten bekanntlich die Merkmale der Blüthen- und Samenfarbe in der ersten und den weiteren Generationen unverändert hervor und die Nachkommen der Hybriden tragen ausschliesslich das eine oder das andere der beiden Stamm-Merkmale an sich.
In Pisum, as we know, the traits of flower and seed colour manifest themselves without alteration in the first and subsequent generations, and the descendants of hybrids exhibit exclusively either one or the other of the two parental traits.
As we know = bekanntlich Mendel may be referring to something that was indeed well known, at least among hybridists. Dominance in flower and seed colour of Pisum had already been observed by Thomas Andrew Knight, “An Account of Some Experiments on the Fecundation of Vegetables”, Philosophical Transactions of the Royal Society of London 89 (1799), pp. 195–204, here 197, and John Goss, “On the variation in the colour of peas, occasioned by cross-impregnation”, Transactions of the Horticultural Society of London 5 (1824), pp. 234–235.
first and subsequent generations = ersten und den weiteren Generationen See p. 33, s. 12.
parental traits = Stamm-Merkmale See p. 16, s. 14.