32 



PHYTOHORMONES 



Fig. 11. Convenient tools for the Avena test. 1, frame for divid- 

 ing agar rectangles into 12 equal blocks with safety razor blade; 

 2, stamp for cutting the rectangles 8x11 mm. from agar disc or 

 sheet 1-2 mm. thick; 3, spatula for application of agar block; 4, cork- 

 tipped forceps for pulling primary leaf loose; 5, decapitation scissors 

 (see Figure 12); 6, forceps for planting in glass holders. 



one side. The curvatures are measured on the resulting 

 shadowgraph (see Figure 22) by means of a celluloid pro- 

 tractor with rotating arm (Figure 13). The angle measured 



is that between the tangent 

 to the extreme curved tip 

 and the straight base. 



Soding (1934) has described 

 a method depending on the 

 same principle, but measur- 

 ing the curvature on the plant 

 itself by placing it over the 

 protractor. 



Fig. 12. Cutting end of decapitation ^^rdy (1921) haS^ devel- 

 scissors. A, adjusting screw to regulate oped a method, which haS 



opening between knives; B, strips of been adopted by Boysen Jen- 



saiety razor protrudmg 4 mm. beyond ^ » 



brass holders C; D, plant being decapi- Sen and by Nielsen, of meas- 

 *^*^^- uring the increased growth on 



