212 



GROWTH OF PLANTS 



FiGUKE 77. Adventitious roots induced with plant hormones. A, Gladiolus corms 

 showing (left) normal condition; {right) adventitious roots induced with /3-indolebutyric 

 acid. B, Tomato plants with tops removed. Left: control having the cut surf ace treated 

 with pure lanohn; right: lanohn preparation containing 1 per cent /3-indolebutyric acid 

 appUed to cut surface of stump. C, Helianthus tuberosus tubers showing control on left; 

 and right: tubers growing adventitious roots 20 days after having been immersed 48 hours 

 in a solution of a-naphthaleneacetic acid (50 mg/hter of water). D, An internal piece 

 of potato tuber induced to root by treatment with /3-indoleacetic acid solution [see publi- 

 cation by Guthrie ^^]. E, Tomato plant treated with the first preparation of a-naph- 

 thaleneacetic acid used as a hormone. F, Camellia cuttings showing natural rooting 

 from callus on non-treated control (left); and right: roots induced along stem of cuttmg 

 dipped into a mixture of /3-indolebutyric acid -f- a-naphthaleneacetic acid, equal parts, 

 making a total concentration of 20 mg per cc of water. 



