SMITHSONIAN MISCELLANEOUS COLLECTIONS 



)5, NO. 20, PL. 



a 



a Glass 4TCna holders, showing position of seedling (lower), position of spring clamp (cen- 

 ter) and general appearance of tip placed against protruding first leaf on decapitated stump 

 (upper). Note: The small tip was displaced through an angle of 90 m order to be shown in 

 the photograph. 



b. A simplified type of Avciia holder designed by L. B. 

 and Organisms, after the completion of the present studie 



Clark, of the Division of Radiation 



