GENETIC CHANGES 211 



the entire orchard. The conditions are comparative and furnish the hasis 

 for a fair comparison of the No. 1418 strain trees with those of the parent 

 variety. 



The yield of the No. 1418 trees in the experimental plant in<,' lias heen 

 more than double that of the comparative trees. The No. 1418 fruits are 

 about twice the size and weight of the comparative fruits. They are more 

 uniformly distributed throughout the tree than is the case with the fruits 

 borne by the comparative trees. Furthermore, the fruits are more uni- 

 form in size, shape and other characteristics than are the fruits of the 

 ordinary variety. So uniform are the No. 1418 fruits tliat they api)ear 

 to have been graded mechanically as to size as they lie on tlie ground 

 after falling. 



The No. 1418 trees appear to be more vigorous growing and develop 

 larger leaves than do the comparative trees. The leaves of the trees of 

 this strain appear to be thicker and have a tougher feel than do the leaves 

 of the trees of the parent variety. In looking down the rows one notices 

 that the larger trees of the No. 1418 strain, with their more luxurious 

 and abundant foliage, stand out markedly as compared w^ith the trees 

 and leaves of the parent variety. 



The fruits of the No. 1418 strain average about 25-30 to the pound as 

 compared with an average of from about 50-60 to the pound as is the 

 case of the fruits of the parent variety. 



The increased size of leaves and fruit and the great vigor of 

 the tree, suggest that in this case a "gigas type" of bud- 

 mutation has occurred rather than change in a single gene. 

 Cytological study might reveal whether this is the case or not. 

 In plants with variegated leaves, such as Pelargonium 

 (Baur) and Coleus (Stout), it is easy to change the racial 

 proportion of green to white or green to colored areas b}' 

 vegetative selection, that is by selection from among the 

 vegetatively propagated offspring of a single mother plant. 

 Apparently in such cases what is varying is the plastid con- 

 tent of the cytoplasm of cells rather than their nuclear 

 structure, but the studies of Emerson and of Hayes u])()n 

 variegation of the seed-coat in maize show that in this case 

 there is a close correlation between the somatic variation 

 (seen in the seed-coat) and the variegated character trans- 

 mitted by the embryo within the seed, so that selection on 

 the basis of the former is attended by genetic change of ;i 

 corresponding sort within the gametes. It cannot be doubted 

 therefore that, in practically all cases of variegation in 



