462 Journal of Agricultural Research voi.xx.No. t 



It will be noted that, even in a saturated atmosphere, the various 

 temperatures had no influence whatsoever on the dormant plants of the 

 trifoliate orange. No growth of the calamondin plants occurred except 

 at 30 C. and in the greenhouse. 



At io° C. no growth of the grapefruit plants took place. It is very 

 evident that at 15 the growth of grapefruit is not only slow but that the 

 growth matures very rapidly. Leaves which mature at this temperature 

 are small, being from one-fourth to one-half the size of the normal grape- 

 fruit leaf. Good growth of the grapefruit plants took place at 20 C. 

 However, the shoots did not grow so rapidly and the maturation of the 

 leaves was faster than at the higher temperatures of 25 and 30 . At 

 these temperatures, where the grapefruit plants were in good condition, 

 a rapid growth took place, the new shoots were longer, and the period 

 over which the maturation of the leaves took place was extensive. To 

 illustrate, at 15 it required from 7 to 8 days for a new shoot to complete 

 its growth, while at 30 , 16 to 20 days were necessary. 



EXPERIMENT 2 



In this experiment plants of the Rusk citrange were substituted for 

 the trifoliate orange. Three plants of the citrange, three of the cala- 

 mondin, and one of the grapefruit were used. One plant each of the 

 citranges and calamondins, in a good growing condition, was chosen for 

 the first group ; one set in which the growth was complete, but with a 

 new bud starting, was selected for the second group; and dormant plants 

 were placed in the third group. Grapefruit plants in good growing con- 

 dition were used. The experiment was carried through in the same way 

 as experiment 1, except that at the end of 15 days the plants in the 5 , 

 io°, and 1 5 C. cases were all transferred to the 30 case under their 

 original bell jars. 



During the 15-day period no growth of the citrange, calamondin, and 

 grapefruit plants occurred at 5 and io° C. (Table VII.) An extremely 

 slow growth was recorded for the grapefruit plants at 15 . Measure- 

 ments of two grapefruit leaves showed an increase in growth of 3 mm. 

 and 9 mm. in length and 1 mm. and 4 mm. in width, respectively, for a 

 period of 15 days. As noted in experiment 1, leaf maturity increased 

 very rapidly at these temperatures, the leaves reaching about one-fourth 

 to one-half the size of those at higher temperatures. 



When the plants held at temperatures of 5 and io° C. were placed in 

 the 30 case, a normal growth for that temperature immediately took 

 place in most instances. The rate of growth of the growing citranges 

 was about 25 mm. per day. The behavior of the dormant plants when 

 transferred to the higher temperatures was erratic. Some immediately 

 responded and started growth, while others remained dormant. 



