The X-Ray Induced Mutation Rate in Pollen in Relation to Dosage and the Nuclear Cycle.

H E haploid cycle of plants offers some distinct advantages to genetic T analysis. Here inheritance is not complicated by dominance relationships, and segregations are much less involved than in disomic inheritance. The greatly simplified problem of rearing large populations and the opportunities in some instances of tetrad analysis are other of the many well known reasons why new inherited characters of haplonts are eagerly sought. The recent work of BEADLE and TATUM (1941) on Neurospora exemplifies the rapid advancement possible in the genetics of haplonts and the interesting uses to which such knowledge may be applied. It has been demonstrated that X-rays applied to microspores of Tradescantia shortly after meiosis induce mutations which are expressed in abortion and changes of size in the subsequently developed pollen grains (RICK 1942). For further understanding of this problem the statistical techniques need elaboration. Also, the response of pollen during stages of the cycle other than the critical stage immediately following meiosis deserves attention. Another aspect to be considered here is the response of these measures of mutation rate to varied X-ray dose.