J. M. BEAL 



i6i 



chyma, continued as patches of meristematic tissue, or infrequently 

 differentiated as small vascular bundles. There was increased activity 

 of the cambium, its derivatives maturing entirely as tracheids. Root 

 primordia were rare. 



Alpha-naphthylmethylacetate applied to the cut surfaces of decapi- 

 tated second internodes of the bean (i) produced in general the same 

 tissue responses as had occurred following the application of most other 

 growth-regulating substances. The production of considerable wood was 

 one of the notable responses. In this respect it resembled the response 

 to a-naphthylacetamide (24). 



Responses of Roots 



Studies of the effects of growth-regulating substances on roots were 

 for a time limited largely to observations on the stimulation or inhibi- 

 tion of root elongation, the development of laterals, and the accompany- 

 ing physiological activities. Some histological and cytological responses 

 of Allium roots to several chemicals were described by Levan (26). 

 Noirfalise (31) reported the cessation of elongation of the primary root 

 of young seedlings of Viciafaba when placed in certain aqueous solutions 

 of heteroauxin. Relatively high concentrations inhibited elongation but 

 resulted in marked increase in diameter and the production of numerous 

 lateral roots. Microscopic preparations showed that the increase in 

 diameter resulted chiefly from the activity of the cells of the pericycle. 

 Morphological changes in induced roots of wheat following treatment 

 with heteroauxin were reported by Burstrom (10). A study of the histo- 

 logical and cytological changes induced in the roots of Allium cepa, 

 Narcissus (var. Paper White), and Tulipa (vars. John Ruskin and Louis 

 XIV) by several growth-regulating chemicals was presented by Carlton 

 (11). Six substances were used: a-naphthaleneacetic acid, indoleacetic 

 acid, indolebutyric acid, /3-naphthoxyacetic acid, a-naphthylacetamide, 

 and tryptophan. These were used at concentrations of 10 or 20 parts 

 per million in a three-salt solution. The bulbs were rooted by placing 

 their bases in water, and when the roots had attained a suitable length 

 the bulbs were transferred to the salt solution containing the respective 

 growth substance. Root elongation was inhibited temporarily by indole- 

 acetic acid and permanently by all the others. The roots of Allium and 

 Narcissus thickened markedly just back of their growing points as a 

 result of treatment with indoleacetic, indolebutyric, naphthaleneacetic, 



