Xenia 211 



arguments for an intercellular transmission of hereditary 

 qualities. But both groups of phenomena are much in 

 need of being critically investigated before they can be 

 reliably employed in this way. The transmission of the 

 hereditary characters of the crown-graft to its stock 15 has, 

 to my mind, never been scientifically proven, and never 

 will be, as long as new experiments are not made, in 

 which the variations of the stock itself, are thoroughly 

 studied and have become well known. Because, until 

 then, the possibility is not excluded that this variability 

 of the stock itself forms the most important factor in the 

 phenomena that have been observed. 



The cases where the pollen is supposed to have trans- 

 mitted hereditary characters outside the fertilized egg- 

 cell and the embryo issuing from it, to the tissues of the 

 maternal fruit, have been carefully arranged by Focke 

 under the name xenia. 16 And his review shows 

 plainly that here one has to deal with exceptional cases 

 which have never yet been thoroughly studied and suffi- 

 ciently controlled. 17 And I think that, without a control, 

 based on critical examination, these data cannot be given 

 that far-reaching significance that would make them the 



15 Cf. the critical summary of the material for observation bear- 

 ing on this point, by H. Lindemuth, Uber Vegetative Bastarderzeug- 

 ung durch Impfung. Landw. Jahrb. 7: 887. 1878. 



16 Focke, Die Pflanzenmischlinge, pp. 510-518. 1881. [See also, 

 Webber, H. J. Xenia, or the immediate effect of pollen on Maize. 

 U. S. Dept. Agr. Div. Veg. Physiol Pathol Bull. 22. Sept. 12, 1900; 

 Correns, C. Untersuchungen iiber die Xenien bei Zea Mays. Ber. 

 Deut. Bot. Ges. 17: 410. 1899. TV.] 



17 The best known instance of Xenia, that of corn, has since been 

 shown to be of a different nature, consisting in the hybridization of 

 the endosperm in the process of double fertilization. See de Vries, 

 Sur la fecondation hybride de 1'albumen. Compt. Rendus Acad. Sci., 

 Paris, 129: 973. 1899, and Sur la fecondation hybride de 1' endo- 

 sperme chez le Mais. Revue generate de Botanique. 11: 129. 1900. 



