June, 11)1 < J Xenia FoUounng Fertilization 275 



planned, especially those of Vilmorin and of Hildebr.\ndt in 

 1867, and of Kornicke (3) in 1872. 



Kornicke's investigations are of exceptional interest inas- 

 much as he concluded that the influence of the pollen is immedi- 

 ately apparent in those races of maize in which the color is in 

 the aleurone layer. Likewise that the effect of xenia does not 

 pass out of the endosperm or appear in any other part of the 

 seed. He went a step further, offering objection to Hilde- 

 brandt's work on the grounds that the color in the races used 

 by HiLDEBRANDT was located in the pericarp and therefore 

 could not appear as the immediate effect of the pollen. 



It is plain, therefore, that nearly ten years before the term 

 xenia was proposed, the need of limiting it to a definite expres- 

 sion occuring in a definite tissue was felt. And even though 

 Focke's interpretation admitted of a wide range of examples 

 and rather indefinite ideas of the nature of this influence, maize 

 became the medium used for the experimental demonstration 

 of xenia, partly due to the fact that the results were easily 

 secured, and partly because those obtained for maize were 

 beyond dispute. This should be remembered in connection 

 with the more modern investigations in endosperm formation 

 and the discovery of triple or multiple fusion. 



In 1899 both De Vries (4) and Correns (5) published papers 

 on xenia. De Vries, who used a pure strain of sweet corn onto 

 which he crossed pollen from a strain of starch corn showed 

 that the kernels exhibiting xenia proved to be true hybrids 

 when grown the second year. In other words, since he was 

 sure that hybridization had not taken place in the races he 

 was using, xenia served as an indicator to separate those seeds 

 which when planted would produce hybrid plants from those 

 which would produce the original pure strain. Correns 

 concluded that the influence of the foreign pollen is limited to 

 the endosperm, affecting only the color or the composition 

 of the reserve food materials. 



Xenia and Triple Fusion. 



On August 24, 1898 Nawaschin (6) reported for the first 

 time before the Russian Society of Naturalists the triple fusion 

 which takes place between the two polar nuclei and the second 

 sperm. This one finds occasionally referred to as "double 

 fertilization," though this name is open to serious objection 



