XENIA IN FOWLS 



Experiments to Determine Whether Cock Has Influence on Color and Form of 



Eggs Laid by Hens to Which He Is Mated Behef 



Seems to be Without Solid Foundation. 



A Review of Some Recent German Work 



XENIA is the name given Ijv 

 Focke in 1881 to designate 

 a curious feature of hybridiza- 

 tion in plants: the direct 

 influence of foreign pollen on the seed 

 l^roduee.d. Popularly, its meaning has 

 been extended to describe any direct 

 infivience on the fruit as well as the 

 seed. Such influence has been a 

 i:)art of farm lore for centuries. The 

 farmer has attributed the bad quality 

 of his watermelons, for example, to the 

 fact that they were pollinated by 

 pum])kins grown in an adjoining field. 

 With the increase of knowledge of what 

 was actually accomplished by pollina- 

 tion, and what the actual process of 

 reproduction was, it became clear that 

 most of these beliefs were little better 

 than superstitions. Genetists decided 

 that the watermelon could not be 

 deteriorated by pumpkin pollen, because 

 that pollen could have no effect on the 

 fruit resulting from the flowers it 

 polhnated. What actually happens is 

 that the germ-cell of the pollen grain 

 unites with the egg cell of the other 

 parent, and the essential parts of the two 

 lie side by side in the resulting seed, not 

 even fusing. It is not until this seed 

 is planted, grows and matures its own 

 seed, that the original heredity-stuff of 

 the ]jarents is shuffled, recombined, and 

 given a chance to ex]^ress new characters 

 or make combinations of old ones. 



Pollen, therefore, in the nature of 

 things, cannot ordinarily have any 

 immediate influence on the fruit 

 produced. But certain exceptions — 

 re])orted for two centuries by farmers 

 and breeders, first examined by Focke, 

 and later well attested by many obser- 

 vers — have been found, the best cxamjjle 

 being in maize. When a race of white 

 maize is crossed with a varic^ty bearing 

 black ears, the seeds produced should 



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all he white. The black father would 

 not show its influence until these seeds 

 were planted and produced ears in 

 turn. But xenia interferes, so that the 

 seeds of our original pollination, in- 

 stead of being white, actual!}' show the 

 effect of the black parent — the\- will be 

 splotched or, in many cases, wholly 

 black. vSpeaking figuratively, xenia 

 seems to leave the pollen parent always 

 one lap ahead in the race. The parental 

 generation shows characters that would 

 not ordinarily be expected until the 

 Fi generation; the Fi generation shows 

 characters that would not ordinarily 

 be expected until the Fo generation; 

 and so on. 



XENIA IN PLANTS 



Here was a mystery that puzzled 

 plant-breeders for some years. Similar 

 phenomena were found in r\x\ buck- 

 wheat, and other plants. The mystery 

 was finallv cleared u]) bv Xawaschin and 

 Guignard (1899) and Wel^ber, Dc Vries 

 and Correns (1900), who found that it 

 could be explained very simph' from a 

 knowledge of the cell mechanism. 

 There are two nuclei in the pollen cell 

 and two in the egg cell. The principal 

 nucleus of the one unites with the prin- 

 ci])al nucleus of the other to ]:)roduce the 

 embryo; the secondar\' pollen nucleus 

 unites with the secondar\' egg nucleus 

 and produces the endospeim or starchy 

 part of the seed. The immediate in- 

 fluence of the pollen parent is therefore 

 naturally to be expected in the endo- 

 sperm, and will be visible, in general, 

 whenever the differences lietween the 

 two ])arents are of a striking nature — 

 black and white, in this ease. In ordinary 

 ])()llinati<)n between i)lanls of like char- 

 acters, an influence is i:)ro(lueed by the 

 pollen ]xirent on the endosperm, but is 



