168 



P. E. Pilet 



___-AM 



I I I — I 



6 CM 



,— L 



PM 



Fig. 1. Guillotine. With the use of this apparatus, the exact root sections (0-0.5; 

 0.5-3.0 mm.) can be easily obtained; the roots, 18 mm. in length, are placed on a 

 grooved (G) plate (PO) with the tips just touching a vertical upright. .\ quick 

 depression of the handle (AM, R) lowers two blades (L) which cleanly cut the 

 roots to size, producing the desired fragments. 



BIOLOGICAL ANALYSES 



Auxin Content 



The extraction of auxins from the roots (an acid fraction of ex- 

 tracts obtained with peroxide-frcc CIICl.,) was carried out as de- 

 scribed elsewhere (11), with subsequent measurements of activity by 

 the Avena test. The auxin content was determined in the two re- 

 gions previously mentioned and expressed (in terms of equivalent 

 lLig. lAA) as a function of the age of the roots (length). Table 1 shows 

 that the concentration of auxins in the meristem is consistently 

 greater than that in the tip. Furthermore, the level of auxins in- 

 creases as the roots age. 



These facts, together with many other observations (12), suggest 



