l62 PLANT GROWTH SUBSTANCES 



and naphthoxyacetic acids, and to a lesser extent in the tryptophan. 

 Roots of Tiilipa showed little enlargement and no adventitious root 

 formation. In Allium and Tulipa proliferation of the pericycle occurred 

 with the formation of numerous root primordia in Allium. Neither true 

 proliferation nor root primordia occurred in Narcissus. 



Responses of Fruits 



Parthenocarpy induced by growth-regulating substances was first 

 accomplished by Gustafson (i8) in 1936 by applying known chemical 

 compounds in lanolin to the pistils of a number of plants. The following 

 year Gardner and Marth (16) reported the induction of parthenocarpy 

 in American holly, Ilex opaca, by spraying the open blossoms with dilute 

 aqueous solutions of several growth substances, including indoleacetic, 

 indolepropionic, indolebutyric, and naphthaleneacetic acids. Gardner 

 and Kraus (15) investigated the histological changes of the pistil of the 

 holly as affected by indoleacetic acid and found that the development of 

 the parthenocarpic fruits paralleled almost precisely that following 

 pollination. The chief differences were that the stigmas of the sprayed 

 fruits proliferated somewhat more than those pollinated, did not collapse 

 and suberize as soon, and developed neither embryo nor endosperm in 

 the ovules. 



Beal (4) appHed i per cent growth substance and lanolin mixtures 

 shortly after anthesis to the cut surface of ovaries of Lilium regale from 

 which the stigmas and styles had been removed by cutting squarely 

 across the top of the ovary at the base of the style. Indoleacetic, naph- 

 thaleneacetic, and naphthoxyacetic acids and a combination consisting 

 of equal volumes of the three i per cent concentrations thoroughly mixed 

 were used. 



Ovaries to which the three, as well as those to which the combination 

 were applied, enlarged in length and diameter at approximately the 

 same rate and attained nearly the same final size. Their length was as 

 great as that of fruits resulting from pollination, but their diameter was 

 always less. Neither apical tumors nor adventitious roots were formed. 



A transection of an ovary at 795 hours (33 days) after treatment 

 showed well-developed carpel walls and ovules. The greater part of 

 the growth had resulted from enlargement of cells, although a few cell 

 divisions had occurred in some regions of both the carpels and ovules 

 following treatment. Again neither embryos nor endosperm were formed. 



