The Linkage Relations of Certain Genes in Oenothera.

One may now predict with some confidence that two characters, which are known to segregate independently in certain Oenothera crosses, will be found to be closely linked in other crosses. Instances of this sort are increasingly numerous. RENNER (1925, 1928) was the first to call proper attention to such differences in linkage relationships, though other cases of the same sort had been discussed earlier by DE VRIES, by RENNER, and by BLANCHARD and BARTLETT. At present there are only two characters that do not show such variable linkage relationships. The better known case involves the flower size differences found in many species (CO, etc. of RENNER 1925). The second is the brevistylis character (short styles and deformed stigmas-b, of SHULL [ 19261) of Oe. Lamarckiana. The two characters are alike in that they have never been found to be linked to any other characters, even when all other characters in a hybrid were linked through the presence of all 14 chromosomes in a single ring.