Scientific Results 



homologue of 'heteroauxin' [indole-acetic acid] was found to 

 be active in causing certain formative responses indicates that 

 possibly other indole derivatives and perhaps other unrelated 

 chemicals might induce one or more of these same responses." 

 It will be seen how abundantly this remark has been justified. 



Description of Methods 



A description of methods may be quoted from a later paper 



from the Boyce Thompson Institute (Zimmerman and 



Wilcoxon, 1935): 



"The compounds were used as distilled water solutions 

 or mixed with lanolin (U.S.P.).^ In a few cases where 

 cuttings were involved dilutions were made with Knop's 

 solution,^ The cuttings were placed in vials or flasks so 

 that the basal ends were immersed in the solutions. The 

 water solutions were introduced into the stems and petioles 

 [the stalks of the leaves] by means of glass tubes drawn to a 

 capillary at one end. The capacity of the tubes varied, but 

 held on an average approximately 0*3 c.c. of solution. The 

 capillary end of the tube was inserted into the stem or 

 petiole and left to drain into the plant. There was consider- 

 able variation in the length of time required for the tubes 

 to empty. Also the response of the plant varied with the 

 rate at which the substance drained from the tubes. 



"Lanolin preparations were applied locally by rubbing 

 the mixture on stems or leaves with a glass rod. . . . The 

 usual concentration range was from o-oi per cent, to 

 2 per cent." 

 Another technique used in later work (Hitchcock and 



Zimmerman, 1936) instead of injection was to dip a slit-up 



portion of the stem of an otherwise intact plant into a vial 



containing solution. 



The following list of species of plants successfully used 



in the experiments reported by Zimmerman and Wilcoxon 



(1935) showed that the effects of certain growth-substances 



^ The lanolin-smear method was introduced by Laibach (1935). 

 ^ Physiologically balanced and isotonic with land-plant cells, Knop's 

 solution is a simple mixture of inorganic reagents in water. 



27 



