UNFRUITFULNESS ASSOCIATED WITH EXTERNAL FACTORS 511 



that constitute what is termed locality and to assign to each its portion of 

 the total influence on fruit setting. This, however, is often difficult and 

 from the grower's standpoint it is only the environmental complex and 

 the plant's response to it that are discernible. Therefore it is suitable 

 to make some mention of the influence of localitj^ in fruit setting, without 

 attempting a detailed analysis. 



The common lilac is said to bear seeds moderately well in England 

 but in parts of Germany its capsules never contain seed.^^ The America 

 grape has been found self sterile in the Experiment Station grounds at 

 Columbia, Mo., though it has been reported perfectly self fertile farther 

 south. "2 Since the immediate cause of self sterility in the American 

 varieties of grape is of two general types — pollen abortion and degeneration 

 in the generative nucleus — locality may be considered to have an influence 

 on pollen development. Acoinis calmnus, when grown in certain parts 

 of Europe, becomes sterile through the degeneration of both pollen grains 

 and embrj^o sacs.^*^ The Jonathan apple is often self sterile in Victoria 

 ( Australia), ^^ though in the United States it is almost invariably self 

 fertile. As self sterility in the apple is due usually to incompatibility or 



embryo abortion, the conclusion seems warranted that it is in one of 

 these ways that the difference between the localities produces this dis- 

 tinctive effect on fruitfulness. 



Still another way in which the factors characteristic of locality influ- 

 ence fruitfulness is in the production of defective pistils. Waugh^'* 

 obtained flowers of the Burbank plum from different sources and found 

 the percentages of defective pistils to be as shown in Table 4. He found 

 all the pistils of Rollingstone defective in flowers obtained from Minnesota 

 City, Minn., and none in a lot obtained from Lafayette, Ind. He 

 observed also that in some seasons certain plum varieties were protogyn- 

 ous in one locality and protandrous in another. 



A case in which self fertilitj^ and fruitfulness vary according to locality, 

 apparently through some influence on compatibility, was mentioned by 

 Darwin. ^'^ He stated that " Escholtzia is completely self sterile in the 

 hot climate of Brazil, but is perfectly fertile there with the pollen of any 



