TECHNIQUE OF AUXIN DETERMINATIONS 29 



rack 



trough 



further work be continued with the same strain.^ Other 

 lines have been used by various workers, perhaps the most 

 notable being Gul Naesgaard in Denmark. 



The standard procedure for the preparation of the plants 

 is as follows: The seeds are freed from their husks (glumes) 

 and soaked in water for 2-3 hours. After this period they 

 are laid out, groove downward, on wet filter paper in Petri 

 dishes in the dark room. They are allowed to germinate 

 in this way for about 30 hours, during which period it is 

 ad\'isable to expose them to some red light, to suppress 

 subsequent mesocotyl growth (Lange, 1927; du Buy and 

 Nuernbergk, 1929). Origi- 

 nally the seeds were planted 

 in a mixture of sand and 

 leaf mould, but more re- 

 cently, for the sake of uni- 

 formity and convenient 

 handling, planting in water 

 has been substituted. If the 

 seeds are to be planted in 



such soil or in washed saw- p^^ § 4^^^^ seedling growing in 

 dust, however, they should glass holder with roots in water con- 

 i . ,1 j.„»,„^„i^^f tained in the zinc trough. The adjust- 



be mserted at an angle of ^^^^^ ^^^^^^^^ ^^^ i^^i^^^^^ ^^^ ^,,„,,.g 

 about 45° with the vertical, 



in order that the shoot may emerge straight. The sand or soil 

 should be so wet that further watering is not necessary, as 

 this will displace the seeds. If, on the other hand, it is too 

 wet the sensitivity of the plants is reduced (Boysen Jensen, 

 1935). The depth of planting is also important and the 

 shoot should be about 8 mm. below the surface ; if too shallow 

 the seeds will be pushed out by the developing roots. 



For water culture convenient glass holders were devised 

 by Went (1928) and a modification of his design is now in 

 almost universal use (see Figure 8). The holders are coated 

 thinly with paraffin, which prevents water from creeping 

 into the guide and makes the fitting of the seeds into the 



> Obtainable from Sveriges Utsadesforening, Svalof , Sweden. 



