TJw N-Arylphthalamic Acids 261 



solutions were applied with a compressed air sprayer and plants were 

 sprayed to the drip point. In other studies, responses equivalent to 

 those from spraying have been obtained by applying 0.01 ml. of 

 each concentration to the apex of the plant (21). Flower numbers 

 were determined after 6 weeks or when the final flower bud was 

 clearly visible. 



Tomato parthenocarpy. Luckwill's test (11) was employed, and 

 0.01 ml. of each solution was applied directly to ovaries of tomato 

 flowers emasculated just prior to anthesis. Six ovaries were treated 

 with each concentration of a chemical. Solutions were prepared as 

 described above, and ovaries treated with 5 per cent acetone did not 

 differ from nontreated ovaries. Ovary diameters were measured to the 

 nearest 0.1 mm. with a vernier caliper 5 days after treatment. 



Avena straight grozath. The procedure used for growing and sec- 

 tioning Avena coleoptiles was that described by Leopold (10) using 

 'Brighton' oats. Coleoptiles 2 to 3 cm. in length were selected and a 

 single 5 mm. section was cut 3 mm. below the tip. The sections were 

 floated, ten to a dish, without removing the leaf, in 10 ml. of the 

 test solutions which contained a phosphate-citrate buffer (pH 5.0) 

 and 3 per cent sucrose (15). Since most of the substituted A''-aryl- 

 phthalamic acids dissolve only with difficulty below pH 6.0, the so- 

 lutions were prepared by dissolving appropriate amounts of each 

 chemical in the K0HPO4 buffer component (pH 8.5) and then adding 

 the citric acid and sucrose. No visible precipitation occurred in 10"^ 

 M solutions prepared in this manner. Lengths of the Avena sections 

 were measured after 20 hrs. to obtain maximum differences between 

 the treated and the control sections (16), and to minimize hydrolysis 

 of the phthalamic acids at pH 5.0 (3). Measurements were made to 

 the nearest 0.5 mm. Elongation was expressed as per cent of the final 

 length of control sections grown in the phosphate-citrate-sucrose 

 mixture. 



Statistical 



The statistical significance of the differences between the means 

 of control and treated samples was based on the "t" test as outlined 

 by Goulden for nonpaired variates (7) . 



RESULTS 



Activity in Tomato Flowering 



In preliminary studies tomato plants were treated with a number 

 of phenyl-substituted N-phenylphthalamic acids at concentrations 

 ranging from 5 to 500 p.p.m. in order to establish an effective range for 

 each. It was found that substitution of chloro- or methyl- groups 



