466 Journal of Agricultural Research vol. xx, No. 6 



EXPERIMENT 4 



It was found in experiment 3 that an alternating day and night temper- 

 ature inhibited the growth of the trifoliate orange, Rusk citrange, and 

 the calamondin plants, while little or no difference could be detected in 

 the rate of growth of the grapefruit at the different night temperatures. 

 To determine the effect on growth of an alternating temperature for longer 

 periods, plants were started at a high temperature, then placed at a low 

 temperature for about three weeks, and then transferred back to the higher 

 temperature 



Two sets of plants in approximately the same condition consisting of 

 one Rusk citrange, one calamondin, and two grapefruit plants (one large 

 plant and one just starting new growth) were used. The first set was 

 retained at 30 C. as a control. The second set after being held at 30 

 for 24 hours was placed in the 15 case for 18 days and then was finally 

 transferred back to the 30 case for approximately 2 weeks. The results 

 of the experiment are given in Table IX. 



