xiv CONTENTS 



Interaction of Growth Substances and Photoperiodically Ac- 

 tive Radiations on the Growth of Pea Internode Sections, 

 by William S. Hillman 181 



Effects of Gibberellic Acid, Kinetin, and Light on the Germi- 

 nation of Lettuce Seed, hy Alan H. Haber and A^. E. Tolbert 197 



Interaction of Growth Factors with Photoprocess in Seedling 



Growth, by William H. Klein ^ 207 



Control of Stem Growth by Light and Gibberellic Acid, by 



James A. Lockhart 217 



Physiological and Morphological Effects of Gibberellic Acid 

 on Epicotyl Dormancy of Tree Peony, by Lela V. Barton 

 and Clyde Chandler 223 



Photoperiodic Effects in Woody Plants: Evidence for the 

 Interplay of Growth-Regulating Substances, by /. P. Nitsch 

 and Colette Nitsch 225 



Section IV Photoperiodic Control of 

 Reproduction in Plants 



The Photoperiodic Process, by James Bonner 245 



Development of Vegetative and Floral Buds, by Ralph H. 



Wetmore, Ernest M. Gifford, and Margaret Cornett Green 255 



Photoperiodic Control of Flowering, hy H. A. Borthwick 275 



Metabolic Aspects of Photoperiodism in Plants, by Irwin Spear 289 



A Correlation of Photoperiodic Response of Xanthium and 

 Germination of Implanted Lettuce Seed, by Lawrence 

 Bogorad and Wayne J. Mcllrath 301 



The Induction of Flowering in Xanthium pensylvanicum 



under Long Days, by /. P. Nitsch and F. W. Went 311 



Dual Day Length Requirements for Floral Initiation, by 



Roy M.Sachs 315 



Chemical Nature of the Photoreceptor Pigment Inducing 

 Fruiting of Plasmodia of Physarum polycephalum, by 

 Frederick T. Wolf 321 



