190 THE THEORY OF THE GENE 



the factors for five other mutant types 1 of Lamarckiana 

 belong in this group, as well as the lethal factors that 

 put these factors in a balanced lethal condition. Accord- 

 ing to Shull the appearance of these recessive characters 

 is due to crossing-over between the members of a pair of 

 chromosomes here identified provisionally as the large 

 central chromosome. 2 



i Kubricalyx buds, and its allelomorph red stem (intensifier), nanella 

 (dwarf), pink-coned buds, sulfur colored flowers, revolute leaves. 



2 Emerson has recently pointed out that the evidence so far published by 

 Shull does not necessarily prove his interpretation of the balanced lethal 

 relation. 



