2 THE THEORY OF THE GENE 



He crossed a tall variety of edible pea to a short vari- 

 ety. The offspring, or hybrids, F x , were all tall (Fig. 1). 

 These were allowed to self-fertilize. Their offspring were 



TALL 



SHORT 



F 1 TALL (SHORT) 



/" 



^. 



1 TALL 



2 



TALL (SHORT) 1 SHORT 



Fig. 1. 



Tall peas crossed to short peas giving in the first generation (F a ), 

 tall peas that are "hybrid," viz., tall (short). The recombination 

 of the gametes (eggs and pollen grains) are shown in the square. 

 Three tall to one short peas result in the next or second (F 2 ) 

 generation. 



tall and short in the ratio of three tails to one short. If 

 the tall variety contains in its germ-cells something that 

 makes the plants tall, and if the short variety carries 

 something in its germ-cells that makes the plants short, 

 the hybrid contains both ; and since the hybrid is tall it is 



