EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 24I 



rather more than usual variation was shown in the rate of germina- 

 tion of seeds from a given capsule. In all the cultures there were 

 seeds that did not germinate until two months after the appearance 

 of the first seedling in the same culture. Nor did the plants from 

 the seeds that germinated late vary more in structure than any of the 

 others. 



One plant that followed exposure of the ovary after pollination 

 with radium of 10,000 activity for 53 hours, never passed beyond the 

 rosette stage. The stem elongated, lifting the rosette about 15 cm. 

 above the surface of the soil, and one very short branch developed 

 on the lower part of the stem (figure 65). The rosette persisted all 

 winter after the plant was removed from the experimental garden to 

 the propagating house, the old leaves dying and new ones forming. 

 But the plant finally died soon after it was photographed in the fol- 

 lowing spring (figure 66). There was here a complete loss of 

 reproductive capacity, and a generally diminished vitality. Careful 

 examination during transplanting failed to disclose any fungus dis- 

 ease or other unfavorable circumstance that might account for the 

 arrested development. 



Among other effects that followed exposure to the rays, the fol- 

 lowing are worthy of mention : 



I. Functional Asymmetry : Figures 67 and 68 illustrate this. 

 These rosettes show a variation in leaf-character which is doubtless 

 not to be attributed to the influence of the rays, falling as it does 

 within the range of fluctuating variability. The asymmetry of the 

 rosette followed exposure of either egg- or sperm-cell, and was esti- 

 mated to occur in about one per cent, of the plants. It may result 

 from either a retardation of growth on one side or an acceleration 

 of it on the other, presumably the former. 



In figure 69, however, is shown an asymmetrical rosette from a 

 seed whose ovary had been exposed for four days to a radmm-coated 

 rod of 10,000 activity. At the close of this exposure the stigma was 

 pollinated with unexposed pollen. In this rosette the leaves on the 

 more vigorous side are crisped, resembling the leaves of O. La- 

 marckiana^ and some other species, but not typical in O. biennis. On 

 the other side. of the rosette the leaves are of the normal biennis type. 

 If we look upon the crisping as an expression of growth-vigor, then 

 the asymmetry of this rosette is logically to be attributed to an accel- 



