o. 



2 



(starch) is laid down instead of a less complex compound ('Schleim,' 

 dextrin?); never the opposite, whereby * * * a simpler substance 

 is laid down instead of a more complicated one.''' B}^ crossing a 

 white dent race with pollen of Black Mexican, a race of sweet corn, 

 McCluer- obtained ears showing xenia in having manj-of the kernels 

 bluish-black and wrinkled like the male parent. The wrinkling of the 

 kernels here would indicate that the starchy endosperm of the Dent 

 race had been modified and become similar to the sugary endosperm 

 of the sweet corn. In describing the xenia produced in this case, 

 McCluer says: 



Ears produced b\' crossing a White Dent with pollen of Black jNIexican ha<l ker- 

 nels varying in color from white to black. More than half the kerhels were wrinkled 

 and had the taste characteristic of sweet corn, while the rest, though showing the 

 black color as much as the wrinkled or sweet kernels, were only less dented than is 

 characteristic of the variety. The taste was not modified. 



In the writer's experiments, however, particularly in the case of 

 dent races with starch}^ endosperm crossed with sweet corn with 

 sugary endosperm, there has been no indication of a modification of 

 the chemical constitution, and while it seems probable that there may 

 be exceptions to Correns's proposition, it would nevertheless seem to 

 hold true in the great majority of cases. 



The experiments and observations of the writer all favor the theory 

 that xenia in maize is caused bj' the fecundation of the emMyo sac 

 nucleus b}^ one of the male nuclei, as suggested by De Vries and 

 Correns, and the evidence now available would seem to indicate that 

 those cases of supposed xenia where the pericarp is influenced must be 

 due to other causes or be explained as errors of observation. Gilta3"'s^ 

 work has done much to clear up this matter, as cited in the introduc- 

 tion, because in no case other than corn was the occurrence of xenia 

 supposed to be so thoroughly established as in peas. In his exten.sive 

 experiments, however, Gilta\^ secured no instance where the effect of 

 the cross showed in the portions of the seed outside of the embryo, 

 and the influence on the em})ryo itself is of course readily understood. 

 The changes in the color of the embryo were visible through the 

 h^^aliiie seed coats, and unless closely examined the color might be 

 interpreted as being in the seed coats. It must be remembered, how- 

 ever, that both Gaertner * and Berkeley,^ in describing instances of 

 xenia in peas which the}- had observed, distinctlv stated that the color 

 is in the seed coats, and it is yet too early to conclude that cases may 

 not occur where the influence is shown outside of the endosperm. 



^ Correns, 1. c, p. 413. 

 ^McCluer, Corn Crossing. I.e., p. 84. 

 ^ Giltay, 1. c. 



* Gaertner, Versuche vmd Beobachtungen iiber die Bastarderzeugung im Pflanzen- 

 reich, pp. 81 and 499. 1848. 



5 Berkeley, Card. Chron., 1854, p. 404. 



