5S6 



THE AMERICAN NATURALIST [Vol. XLVI1I 



these, or SxsX. Assuming a chance recombination of 

 these factors in the gametes derived from these synthetic 

 horny seeds, the gametes will be of four kinds. Both the 

 sweet and the waxy may be present (SX) or the sweet 

 may be present without the waxy (Sx), or the waxy with- 

 out the sweet (sX), or both may be absent (sx). At ferti- 

 lization each of these kinds of gametes may unite with 

 any one of the four corresponding kinds derived from the 

 other parent, producing 16 zygotic combinations. In the 

 diagram the four classes of gametes from one parent are 

 given in the horizontal row at the top, and the same four 

 classes from the other parent in the vertical row at the 

 left. Each gametic combination from the top is repeated 

 four times in the squares below, while each combination 

 at the side occurs four times in the corresponding hori- 

 zontal row of squares. Thus each of the squares repre- 

 sents the result obtained by combining the gametes repre- 

 senting the horizontal and vertical rows that intersect at 

 that point. In all cases where both S and X occur together 

 the seed should be horny, where only 8 occours the seed 

 should be sweet when only X occurs it. should be waxy, 

 and in one square (Xo. 16), where neither S nor X occurs 

 there is a new combination which the results have shown 

 to be a new type of sweet seed, indistinguishable from 

 ordinary sweet seed but behaving differently when crossed 

 with other types of endosperm. 



In accordance with the above analysis the expected re- 

 sults in the third xenia generation were as follows : 



