PLANT HYBRIDIZATION BEFORE MENDEL 355 



"The hybrids accordingly appear, on the crossing of certain varieties 

 of Pisum sativum, to gain an access of height, in comparison with the 

 paternal and maternal variety grown from self -fertilized products; with 

 other combinations, on the other hand, such an advantage of crossing, as 

 compared with self-fertilization, is lacking, and there is merely to be 

 found an influence of the paternal variety on the height of the hybrid." 

 {lb., p. 531.) 



Further, it is stated: 



"with respect to the relative influence (or the relative weight) of a 

 difference in the height-character of the paternal and the maternal va- 

 riety, my conclusions furnish the following : 



"The higher type prevails, indifferently as to whether it is due to the 

 father or the mother. The derivatives of a relatively low variety, after 

 pollination with the pollen of a relatively high one, appear, as Andrew 

 Knight already observed, relatively strongly increased in height. In the 

 reverse case, the hybrids are generally little, if at all, lowered in height." 

 {ib., p. 532.) 



The attitude of mind prevailing at the time of the discovery of 

 Mendel's paper, is singularly brought out even in the paper of 

 von Tschermak, in the following form of statement : 



"in the seeds of the hybrids [Mischlinge], obtainable in the first gen- 

 eration from self-fertilization, the characters yellow and smooth, evi- 

 denced themselves precisely as in the case of the cross-pollinated seeds 

 of the mother plant, as being of higher value or hereditary potency, than 

 the characters green and wrinkled, while in the case of the artificial 

 breeding of products of heteromorphic xenogamy the first-named char- 

 acters are almost exclusively dominant: the latter, 'recessive' ones, only 

 come to light pure in individual cases (or as admixture) ; those characters 

 in the seeds of the first hybrid generation attain, only in the majority of 

 cases, to development pure ; in the minority of cases, the 'recessive' char- 

 acters appear. 



"In the first case, there exists an almost absolute dominance ; in the 

 second a mere prevalence (in certain relationships)." {ib., pp. 534-5.) 



This statement appears to show that, in the investigator's mind 

 at that time, the old idea of a sort of "prevalence of potency" 

 existed, which, in what we now call the F^ generation, gave 

 almost exclusive dominance ("bei der kiinstlichen Erzeugung von 

 Produkte hetermorpher Xenogamie, die erstgenannten Merkmale 

 fast ausnahmlos dominierend sind, die letzteren, 'rezessiven,' nur 

 in Einzelfallen rein, [oder als Beimischung] zur Tage treten," 

 etc.). {ih., p. 535.) 



However, in what is now known as the Y^ generation, referred 

 to by von Tschermak as "an den aus Selbstbefruchtung erhal- 

 tenen Samen der Mischlinge in erster Generation" (p. 535) » it is 



