OTHER ACTIVITIES OF AUXINS 



223 



swellings have their counterpart in the formation of callus 

 at the basal cut surface. Such callus formation, which in- 

 volves both cell enlargement and di\dsion, was observed in 

 Acalypha cuttings by Bouillenne and Went (1933) after 

 appUcation of diastase or extract of rice polishings. They 

 concluded that the callus was caused by a special substance, 

 analogous to, but probably not 

 identical with the root -forming 

 hormone. 



It was reported by Laibach 

 (1933) that orchid pollinia, ap- 

 plied to decapitated epicotyls 

 of Vicia Faba, cause a marked 

 increase in thickness. The same 

 result was obtained on other 

 plants by Laibach, Mai, and 

 Muller (1934), Mai (1934), and 

 Miiller (1935), both with orchid 

 pollinia and with ether extracts 

 of these and of urine. ^ Later the 

 same effect was obtained with 

 pure indole-3-acetic acid in lano- 

 Une by Laibach (1935) (see Fig- 

 ure 60), by Hitchcock (1935), 

 the authors (u), and others, 

 while similar results from the 

 application of indole-but}Tic, 

 naphthalene-acetic, and other acids have been mentioned by 

 Zimmerman and Wilcoxon (1935). 



The only quantitative work so far carried out is that of 

 Laibach and Fischnich (1935a) on swellings, and of Rogen- 

 hofer (1936) on callus proper. The former found that the 

 extent of thickening of Vicia Faba epicotyls is proportional 

 to the logarithm of the concentration of auxin applied, using 

 lanoline paste. Rogenhofer determined the callus produced 



Fig. 60. Swelling and callus 

 formation at apical cut surface 

 of decapitated epicotyl of Vicia 

 Faba, after treatment wdth in- 

 dole-acetic acid paste. (From 

 Laibach, Ber. d. hot. Ges. 53: 

 359-364, 1935.) 



1 These workers proposed to call the active substance causing swellings " Meris- 

 tine," but since it is identical with auxin the name can be dropped. 



