Reproduction 365 



dandelion ; and there are similar instances among hawk- 

 weeds, meadow rue, Alchemilla, and several other genera 

 of flowering plants. In fact, if we examine the cases re- 

 ported for all plants, both higher and lower, we find that 

 parthenogenesis, or that which is here included under that 

 term, is not uncommon. Development without fertili- 

 zation is a well-established phenomenon in certain insects 

 and other lower animals. There are also some extremely 

 interesting cases of what has been termed artificial par- 

 thenogenesis, reported by Loeb, Lefevre, and others. 

 In the latter the artificial development of the egg-gamete, 

 without fertilization, is induced by chemical or physical 

 stimuli. When there is no tendency toward natural 

 parthenogenesis, this artificial stimulation of development 

 has never gone so far as to produce adult individuals, but 

 larval stages have been successfully reared. 



215. Xenia in corn. The appearance of the seed 

 gives usually no indication of the pollen which was effective 

 in fertilization. In corn, however, the observation was 

 recorded nearly two centuries ago that certain colored 

 sorts planted together " will mix and interchange their 

 colors " ; that is, in the seed of the first year there will be 

 mixed colors. Numerous carefully conducted experiments 

 in recent years by De Vries, Correns, Webber, and others 

 now clearly demonstrate the immediate effects of the pollen 

 in corn, and a physiological explanation is at hand. 



215 a . Indications of xenia. - We may first note the re- 

 sults of xenia. If pollen of the black Mexican or Cuzco 

 varieties, forms possessing a bluish-black aleurone layer, 

 are applied to the silks of white or yellow sorts, many of 

 the seed resulting show the blue-black color of the pollen 



