nybom: vegetativelv propagated species 



273 



Figure 10. — Gamma-ray -induced mutation in Cox's Orange apple ivitli 

 increased red over-color. Normal apple to the left. 



built up as more or less stable periclinal chimaeras. Some of them 

 make trouble by being too labile, like the reverting Starking Deli- 

 cious (20), while others may be very constant. Such "ectochimaeras" 

 (Figure 12), as for example thornless blackberry sports (26) or types 

 with tetraploid epidermis (36), have normally not been accessible for 

 further breeding work, because, as Darrow (26) says, "unfortunately 



Figure 11.— Neutron-induced sectorial mutation with increased red color 

 in Cox's Pomona apple. The first two rows represent the fruits from an 

 affected branch, still sectorial and unstable. The other two rows from 

 normal branches. 



