MENDEL'S LAW. 279 



It is very probable that marry supposed new characters are merely 

 the peculiar result of the blending of opposite characters, neither of 

 which 'dominates' the other; or it may be that the blending of two 

 unrelated dominant characters gives rise to new characters. As an 

 instance of how this might occur, the presence of two chemical sub- 

 stances, one derived from each parent, might give new flavors in fruit, 

 or new colors in flowers. Bateson has demonstrated a case of the 

 latter and shown that the new and radically different color is not a new 

 character at all, but a blending of parent characters which obey 

 Mendel's law perfectly. 



Is it not possible that Mendel has also shown to us an explanation 

 of bud sports? These sports are notoriously common on plants known 

 to be hybrids. May not the separation of parent characters occa- 

 sionally occur at stages of growth other than the formation of germ 

 cells ? If such is the case, bud sports at once come under the law. 



It does not seem improbable that, once in a while, the parent char- 

 acters might fail to separate in the usual manner on the formation of 

 germ cells, so that we might have a few cells inheriting both of a pair 

 of opposite characters, and this might extend over a series of genera- 

 tions before the separation finally occurred. Under such conditions, 

 a recessive character might be carried over any number of generations 

 without showing itself, finally cropping out and giving a case of 

 atavism. Perhaps this is the explanation of atavism. It would be 

 interesting in this connection to know if atavic characters are 

 ordinarily recessive. 



It is clear that we have before us a working hypothesis that offers 

 a possible explanation of a large number of phenomena^ heretofore 

 absolutely inexplicable. It will require time to test the hypothesis, 

 even in the limited number of cases suggested above. 



The only data thus far published in this country that may be 

 used as a direct test of Mendel's theory are those I secured from 

 hybrid wheats.* At the time these data were arranged for publica- 

 tion similar work in Europe was unknown in this country; they 

 were merely arranged to show that similarly bred hybrids split up 

 into the same types, each type tending to occur in a definite proportion. 

 In all my hybrids characters were present that apparently separated 

 in a manner different from that called for by Mendel's theory. For- 

 tunately, however, the data referred to may easily be arranged to test 

 the applicability of this theory to two characters, namely, beards and 

 velvet chaff. In five out of fourteen crosses one parent was bearded 

 and the other smooth, two of the five being reciprocals. Beards 

 being recessive, theory would call for 25 per cent, of bearded plants 



Bui. 115, Off. Ex. Sta. U. S. Dept. Agr. 



