138 Plant Tissue Culture 



sufficient number of replications is provided, the 

 results can be counted on to be, under like condi- 

 tions, similar from one test to another and, after 

 properly correcting for regular seasonal differ- 

 ences (see later), they will give comparable results 

 from year to year and from season to season. 



The setting up of stocks for all cultures involves 

 essentially the same procedure. The prime requi- 

 sites are a considerably greater amount of avail- 

 able material than is at all likely to be needed so 

 that a selection is possible, all material to be of 

 clonal origin. Callus cultures grow much more 

 slowly than do root cultures, so that a greater 

 time, usually about a month, must be allowed 

 between the setting up of stocks and their actual 

 utilization. 



Inoculation. The procedure in making inocula- 

 tions is comparatively simple. The whole pro- 

 cedure is carried out in the transfer room. Stock 

 cultures from which tips or callus fragments are 

 to be taken are placed in a tray to the left of the 

 operator. The instruments are in the sterilizing 

 beaker or pan, in front of him (Fig. 30). Unin- 

 oculated flasks of nutrient are placed in trays to 

 his right and a box for discarded caps stands at 

 his left. The glass caps are removed from both 

 sets of flasks. A flask containing a stock culture 

 is grasped in the left hand, tilted to reduce the 



