ILLUSTRATIONS 



Facing 

 Figure i Page 



Natural aerial roots, forty feet long, of a tropical vine 

 growing in the Missouri Botanical Garden, St. Louis, 

 U.S.A. 30 



Figure 2 



Tomato plants with i8-day-old roots on stems and 

 leaves. --------30 



Figure 3 



Collar of white roots on the upper part of the stem 



of Kalanchoe daigremontiana - - - - 30 



Figure 4 



Cuttings of American holly, showing roots produced 



five weeks after treatment with indole-acetic acid - 31 



Figure 5 



Cuttings of American holly, showing roots induced 



by treatment with naphthyl-acetic acid - - - 31 



Figure 6 



Sketch indicating no, medium, and maximum 

 response of split stems in Went's pea test - - 131 



FORMULA DIAGRAMS 



Conjugations of phenol ------ 72 



Analogues of indole ___--- 82 



Auxin-a, indole-acetic acid, creatinine, and creatine - 88 

 Indole and some derivatives - - - - 101-103 



The auxins -------- 113 



Vitamins Bi and C « - - - - 115-116 



