Interaction in Polyhybrids 



333 



or two T genes. The Fi and F2 "palm" plants are T-0-; the 

 "oak-tongue" type is tt 00. Other genes may also interact with 

 these to give still different types. The type known as "fern" 



Fig. 94. Gene interaction in Primula. An oak-leaved plant, 00 TT 

 {upper left), was crossed with a tongue, 00 tt {upper right), to form a 

 palm type, Oo Tt {upper center). The F2 segregated into the four types in 

 the bottom row from left to right: 9 palm {0 T) : 3 oak {o T) : 3 tongue 

 {0 t) : 1 oak-tongue (o 0. (Photograph by Dr. W. Brooks Hamilton from 

 herbarium material furnished by Dr. Edgar Anderson.) 



(Fig. 95) has narrower leaves than the "palm"; the clefts are 

 arranged as in a typical fern leaf. Such plants are produced by 

 the genes yy in cooperation with the dominant genes T and 0. 



