294 MUTATION AND PLANT BREEDING 



petiole. They are, therefore, not chimaeric in structure but represent 

 homogeneous changes. 



Dermen: What is the chimeral make-up of yellow variegation in the 

 pear? 



Nybom: I believe the pear clone in question has normal epidermis 

 and second layer and a chlorophyll deficiency in the third cell layer. 

 It remains to be investigated further, however. 



