SECRETARY'S REPORT 187 



carbon-14 produced by thermonuclear devices. It is assumed that the 

 carbon dioxide in the water as it entered the ground-water system 

 was in isotopic equilibrium with the atmosphere, and that the carbon 

 dioxide the water picked up as it percolated into the ground-water 

 system was from recently decayed organic material. Thus, the re- 

 charge water would have a carbon-14 age of less than two years. 

 Measurement of the carbon-14 content of water near the recharge area 

 bears out this assumption. It is further assumed that exchange of 

 carbon dioxide with older carbonate in the system is insignificant. 

 The resultant data for water from a particular locality will be the 

 average travel time of the water from the recharge areas to the sample 

 locality. In the cases studied, water requires less than 10 years to get 

 from the top of the mountain as rain to the main ground-water system 

 at the base of the mountain. 



The simultaneous measurement of spectral quality regions of sun 

 and sky radiation as perceived by a horizontal flat receiver is progress- 

 ing. Technical difficulties encountered in automating the recording 

 system have been largely overcome or corrected by modification and 

 adaptation. We expect to achieve a continuous operation by early fall. 



Preliminary experimental data from plant material have been 

 obtained, primarily to test the operation of the growth rooms and 

 greenhouse. These results indicate that, within specified limits, the 

 growing rooms and greenhouse area can be controlled and made uni- 

 form with each other in respect to light intensity, temperature, carbon- 

 dioxide content, and day length. The photosynthetic rates of the plant 

 material in the three areas, as measured by dry-weight production, 

 are uniform, indicating that the physical control system operates 

 effectively. 



PUBLICATIONS 



Klein, Willl&^m H. ; Price, L. ; and Mitrakos K. Light stimulated starch de- 

 gradation in plastids and leaf morphogenesis. Photochemistry and Photo- 

 biology, vol. 2, pp. 233-240, 1963. 



Mitrakos, K. Chlorophyll metabolism and its relationship to photoperiodism, 

 endogenous daily rhythm and red, far-red reaction system. Photochemistry 

 and Photobiology, vol. 2, pp. 223-231, 1963. 



Price, Leonard ; Mitrakos, K. ; and Klein, W. H. Photomorphogenesis and 

 carbohydrate changes in etiolated leaf tissue. Quart. Rev. Biol., vol. 39, 

 pp. 11-18, 1964. 



SiQALOVE, Joel J., and Long, A, Smithsonian Institution radiocarbon measure- 

 ments I. Radiocarbon, vol. 6, pp. 182-188, 1964. 



OTHER activities 



The division was represented during the year at a number of sci- 

 entific meetings. In attendance at the American Institute of Bio- 

 logical Sciences meeting in August at the University of Massachusetts, 

 Amlierst, Mass., were J. L. Edwards, R. H. Gettens, Dr. W. H. Klein, 



