to provide more than an indication that there are more aberrant chromosomes among irradiated shrubs than among nonirradiated. There is also the problem of finding nonirradiated populations of shrubs with certainty. Much of the area east of both Yucca and Frenchman Flats, even though they may presently show essentially background radiation levels, may have been irradiated by fallout from the early aboveground tests. Because of the long lives, most of the individual shrubs present today are those that were present 20 to 30 years ago. If, by going outside the localities, one tries to avoid the possibility that "nonirradiated" populations might have been irradiated in the past, then there is the possibility that genetic variability may become a factor. Despite this, it appears worthwhile to look at other populations also, and this will be attempted in the future. Annuals continue to be of primary interest to this project, but unfavorable growing conditions appear to prevail, and consequently there probably will continue to be a dearth of material for examination. SUMMARY AND CONCLUSIONS Chromosomal abnormalities within populations of Artemista sptnescens were found with a low frequency in both irradiated and "nonirradiated" plants (selected plants outside the presently known radiation areas) from Plutonium Valley, Area 11, NTS. The frequency of abnormalities appears to be somewhat higher in the irradiated population than in the nonirradiated. More cells need to be examined before this conclusion can be considered firm. Despite the possible complication of variation due to genetic variability among different localities, other populations of Artemtsia should also be evaluated. Because of the likelihood of radiation exposure to many generations, annual species remain a prime objective of this investigation. CY 1976 appears to be another year in which annuals will be sparse or absent from some areas of NTS. 118