CONTENTS 



Paper ' P*oe 



XIX. Photoperiodism 677 



W. W. Garner, Principal Physiologist in charge of Tobacco and 

 Plant Nutrition, Bureau of Plant Industry, U.S. Department of 

 Agriculture, Washington, D.C. 



XX. Plant Growth in Continuous Illumination 715 



John M. Arthur, Biochemist, Boyce Thompson Institute for Plant 

 Research, Inc., Yonkers, N.Y. 



XXI. The Effects OF Light Intensity upon Seed Plants 727 



Hardy L. Shirley, Associate Silviculturist, Lake States Forest 

 Experiment Station, University Farm, St. Paul, Minnesota 



XXII. Effects of Different Regions of the Visible Spectrum upon 



Seed Plants 763 



H. W. Popp, Associate Professor of Botany, Pennsylvania State 



College, State College 



F. Brown, Instructor in Botany, Pennsylvania State College, State 



College 



XXIII. Effect of the Visible Spectrum upon the Germination of 



Seeds and Fruits 791 



William Crocker, Managing Director, Boyce Thompson Institute for 

 Plant Research, Inc., Yonkers, N.Y. 



XXIV. The Effects of Visible and Ultra-violet Radiation on the 



Histology of Plant Tissues 829 



J. T. Buchholz, Professor of Botany, University of Illinois, Urbana 



XXV. Some Infra-red Effects on Green Plants 841 



John M. Arthur (see Paper XX) 



XXVI. The Effect of Ultra-violet Radiation upon Seed Plants . . 853 

 H. W. Popp and F. Brown {see Paper XXII) 



XXVII. The Effects OF Radiation on Fungi • 889 



Elizabeth C. Smith, Research Assistant, University of Wisconsin, 

 Madison 



XXVIII. The Problem of Mitogenetic Rays 919 



Alexander Hollaender, Research Associate (under auspices of 

 National Research Council), University of Wisconsin, Madison 



V 



