4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



The next to the most hair roots were in f 20 ; next to thickest coleop- 

 tiles in £25/20. Greatest percentage (76.4) germination was in £25/20. 



The most growth by weight o£ roots and shoots o£ all seedlings 

 occurred in £25/20 (15.9) and in C25/20 (14.5) ; least growth by 

 weight (4.4) in £20/40; next to lowest, £25 (7.1). 



All seeds were germinated in contact with nutrient solution (4), 

 £or it was £ound that roots £unction immediately as they £orm ; and in 

 their £unctioning affect immediately the growth o£ the seedlings with 

 the materials they chance to meet. 



The above observations were made on several occasions incidental 

 to a study o£ the optimum conditions for obtaining coleoptiles o£ uni- 

 form reactivity phototropically. They are more a contribution to the 

 discussion of the subject of standardization of the conditions of growth 

 in plant physiology than announcement of new phenomena established. 

 This study has been interrupted and the critical repetition of the 

 observations for the time being intercepted. 



The experiments, though incomplete, have led me to the following 

 conclusion : that the conditions for optimum growth and for greater 

 uniformity of phototropic response involve (i) contact with nutrient 

 solution; (2) radiant energy of extended wave lengths — at least dif- 

 ferent wave lengths at different stages of growth ; (3) a wave of tem- 

 perature rather than constant temperature ; (4) perhaps darkness as 

 well as light ; and (5) proper atmosphere. 



I express appreciation to Secretary C. G. Abbot for the facilities 

 and opportunity placed at my disposal to carry on this work, to Dr. 

 E. S. Johnston, assistant director of the Division of Radiation and 

 Organisms of the Smithsonian Institution, and to members of the 

 Staff' of the Division. 



LITERATURE CITED 



(i) Johnston, Eaul S. 



1934. Phototropic sensitivity in relation to wave length. Smithsonian 

 Misc. Coll., vol. 92, no. 11, pp. 1-17. 



(2) Flint, Lewis H., and McAlister, E. D. 



(To be published.) The action of radiation of specific wave lengths 

 in relation to the germination of light-sensitive lettuce seed. 

 Compt. Rend. Assoc. Internat. Ess. Sem., Copenhagen. 



(3) WiNTON, A. L., and Winton, Kate B. 



1935- Structure and composition of foods. J. Wiley & Sons. 



(4) Johnston, Earl S., and Dore, W. H. 



1929. The influence of boron on the chemical composition and growth 

 of the tomato plant. Plant Phys., vol. 4, no. i. pp. 31-62. 



