PLANT HYBRIDIZATION BEFORE MENDEL 341 



F4: 



224 yellow 216 yellow 225 yellow 70 green 307 green 



(23-89%) 

 Experiment II 



Late green Erfurt "Folgeerbse" with green cotyledons, and 

 "Bohnenerbse" with yellow cotyledons. 



Fi 31 yellow (12 planted) 



Fa 



775 yellow 247 green 



(21 planted) (20 planted) 



292 green 462 yellow 149 green 670 green 



(23.6%) 



Correns holds (p. 164) that the separation of dominant and 

 recessive factors (Anlagen) takes place at the earliest, on the 

 laying down of the primordia of the ovules and stamens, and at 

 the latest, on the first nuclear division in the pollen grain, and in 

 the division at which the primary embryo-sac nucleus is formed. 



As to the fact that, when the hybrid in the Fj^ generation, in- 

 stead of being self-pollinated, is pollinated with pollen from the 

 dominant parent, its progeny is half dominant pure, and half 

 dominant, but giving progeny 3: 1 dominant and recessive; and 

 that when an F^^ hybrid is pollinated by the recessive parent, it 

 gives a progeny one half of which is recessive, the other half 

 dominant, but producing progeny 3 : 1 dominant and recessive ; 

 Correns states (p. 165) : 



"This theoretically derived rule I find realized in my maize crosses." 



Correns shows in this first paper a full insight into the signifi- 

 cance of the following rule of Mendel : 



"it is thereby proven at the time, that the behavior of every two differ- 

 ing characters in hybrid combination is independent of the differences 

 otherwise in the two parent plants," 



by the statement in a note (p. 166) that, 



"Even this rule does not hold in general; there are races with coupled 

 characters." 



This is, for the time, knowledge in advance of the then state 

 of investigation with respect to Mendelian behavior. 



Moreover the later work of Bateson on hybrids of sweet peas, 

 involving pollen grains of different shapes, is already forecast 

 by Correns in the statement (footnote, pp. 166-7) • 



