Flowering 255 



in 1935. The data were published later by Lewcock (1937). The dis- 

 covery that auxins could also force flower initiation was first made in 

 Hawaii in 1937, and was published five years later (Clark and Kerns, 

 1942). These workers found that the application of small amounts 

 of auxin onto vegetative pineapple plants caused the formation of 

 flower buds, and the application of relatively large amounts of auxin 

 onto plants which would normally be expected to flower prevented 

 flowering. These opposite qualitative responses to auxin are shown in 

 figure 105. It can be seen that plants treated with 10 or 50 mg./l. of 

 naphthaleneacetic acid in August came into flower whereas the control 



z 



UJ 



o 



I- 

 z 

 liJ 

 o 



cr 



LU 



1000 MG/L 



CONC. OF AUXIN 



Fig. 105. The effects of sprays of various concentrations of auxin (naphthalene- 

 acetic acid) upon flower initiation in the pineapple, showing 100 per cent forcing 

 of flowering by weak concentrations applied in August, and complete inhibition 

 by strong concentrations applied in November (data of Clark and Kerns, 1942). 



