wo §& « high level of irradiation. The cells of the growing points enlarge; the cytoplasm in the oslls become less denses the eel] walls thicken. the region takes on a somewhat abnormally mature appearance, In short, The other grewing regions af stems and roots are similarly affected by radiation. However, the cell's apical meristems appear to he damaged when the plants are grown in solutions whose specific activity level was low enough te afford normal development of the rest of the plant. By measuring the sige of the peripheral apical seristenatic cells under a migcroscope 1% has been possible to observe effects or irradiation from 50 wicrocuries of PJ2 per liter of ‘nutrient solution dewn to less than 2 microouries. This is a range of activity over which there is oo apparent change in the size of the plant. These results indicated that this method will serve as a quantitative measurenent of the effect of irradiation on plants at relatively low eotivities. It haa thus been possibile to show thate ven at the lower Yadiation levels thera is m effact on plant growth, oe Civil DefenseLialsan*Branch Civil Defense Legislation - A meuber of the Branch attended the hearings held by Sub-committee of the Senate irmed Services Comnittes on proposed éivil defense legislation. On Decamber 8 et the request of this gub-comslttee the Director of the Division of “ivlegy and Hedinine testified on the pending bilL, His statexent hoe Seen cizeplated for the information of the Commission aa AEC 171/15 dated December 18, 1950. Subjest to a request to the Chairwm, iC, by Reprasentutive Whittington, Chairmen of t he House Public Works Committees, the Director of Biolory and Medicine and the Acting Chief, Civil Defense Lisivon Breneh, net with Mr. Whittington and Jeprasentative Dondero to diseases effects of atomic weapons relative te pending legislation for dispersal of Federal agencies. — Shelters for AZC Facilities (QeSal Use OnLy? Major AZS installations have been requested throngh the operating program divisions to furnish "flash" estimates of the costs involved in providing adequate shelters for their populations, assuming enemy air attacks with ateate as well as other types of weapons, and warning syatema capable of transmitting signals of such attacks to the populations involved. To assist in formulation of these estinstes tentative design eriteris for communal type shelters and rough sketches af suggested familytype shelters were furnished as guides. Desicn Criteria for Savannah River Plant The Acting Chiof, Civil Defense Liaizen Branch, spent a major portion of his tine during the month working with representatives ofthe Division of Production, the Department ef Defense and the Dopont Company in determining design critoria for the new Savannah River Plant. OFFICE >