Radioactivity-contaminated areas where morphological or phenological effects are not observable are of interest from another point of view, however, particuIn some larly where there have been low-level doses for one to two decades. areas, these accumulated doses approach levels associated elsewhere with Site D, Area 11, NTS, which is the subject of this morphological effects. It is contaminated by plutonium spread primarily by a study, is such an area. nonnuclear high explosive, although there was also a small component of nuclear fission debris accompanying the distribution of plutonium. In the absence of obvious phenological or morphological changes, it would be informative to look for possible radiation effects at the cytological level or, more precisely, at the chromosomal level of organization in cells. At this level, radiation damage can sometimes be inferred from possible hindrance of production or germinability of seeds. However, a more direct method of investigating possible radiation damage is examination of the chromosomes themselves under a light microscope, where certain radiation effects have been noted for some decades prior to the development of nuclear energy or the use of nuclear explosives. At Area 11, NTS, where safety tests were conducted in 1954 and 1955, dosimetry was set up and doses were estimated to range from 35 to 140 R in the particular area of interest to this study (Rhoads and Franks, 1975). In this area, a large but uncertain number of generations of annual plant species have been irradiated at all stages of their life cycle. For this reason, the annuals were, and continue to be, of special interest. However, due to the time of precipitation, there were almost no annual species produced in either 1974 or 1975, even though many species of annuals occur there in large numbers in more favorable years. Radiation effects on native shrubs at the cytological level have not been investigated either. Area 11 is dominated by the shrub species Atriplex conferttfolta, although several other species also occur, among them Artemisia spinescens, Grayia spinosa, and Eurotia lanata. METHODS Cytological investigation requires that cells be collected at precisely the right time in order to see chromosomes with a light microscope, that is, at a time when chromosomes occur in a nondiffused condition within cell nuclei. These conditions are met at Metaphase I, before final division in the production of pollen cells found in the anthers of developing flower buds. Since none of the NTS species appear to have been the subject of cytological investigations, other than chromosome counts on some, there are no guidelines for flower bud collection to ensure finding the proper developmental stage. Among the five species of shrubs whose flowers were collected, only one, a Compositae, Artemisia sptnescens, had cells at the proper stage for examination, with N (number of chromosomes after meiosis) equal nine. This report is restricted to that species and plant material collected in Plutonium Valley, Site D, in Area 11, NTS. Ten year radiation doses to shrubs 112