128 



GROWTH HORMONES IN PLANTS 



Hitchcock, 1933a, h). The effects of 16 different "growth sub- 

 stances" appUed to stems and leaves either in the form of paste or 



Fig. 42. — Rooting and nastic responses obtained by applying synthetic sub- 

 stances to Lycopersicon. A, left: control plant, decapitated; right: plant with 

 surface of cut stem treated with 1.0 per cent a-naphthalene acetic acid; photo- 

 graphed after 8 days. B, left — control plant; right — plant after injections of 

 0.01 per cent indole butyric acid, photographed after 14 days. Note induced 

 epinasty of leaves and adventitious roots. {From Zimmerman and Wilcoxon, 

 1935.) 



in sohitions have been considered in relation to the local initiation 

 of adventitious roots on these organs (Figs. 41 and 42) (Zimmer- 

 man and Wilcoxon, 1935). a-Naphthalene acetic acid and 



