482 Journal of Agricultural Research voi.xx, N0.6 



plant at the end of 8 days, and on the trifoliate orange and citrange plants 

 within 20 days. One month after inoculation several tiny spots ap- 

 peared on the leaves of one ealamondin plant. This was the only suc- 

 cessful infection of this species at 20 during the course of the work. 



At the end of the first month, the plants held at 15 C. were transferred 

 to the 30 case, and the set kept at 20 was abandoned. Four days 

 after the plants were transferred to the higher temperature all were 

 diseased, having from several to many spots. By the end of two weeks 

 the disease was general on all the plants. The spots were more or less scat- 

 tered and typical and not at all like those described in experiment 2 a. 

 However, this was due, in part, to the fact that the leaves of the plants 

 used in this experiment were from one-half to three-fourths grown, 

 while the foliage of the others was mature except for the small unfolding 

 buds. The results obtained are the some as those reported on in experi- 

 ment 2 a, except that in this case the plants were held at the lower tem- 

 perature 1 month instead of 15 days. Table XIV gives the total number 

 of spots with part of the plant attacked at the temperature of 20 for 

 one month and for two weeks after transferring the plants to the 30 case 

 from a temperature of 15 . 



EXPERIMENT 3A 



According to the results of experiment 3, a varying day and night 

 temperature had no appreciable effects on the development of the grape- 

 fruit plants. On the other hand, the effect was noticeable on the growth 

 of the other plants used. Thus, in this experiment, canker occurred at 

 all temperatures on the grapefruit plants, as can be seen in Table XV. 



On the ealamondin plants held at the constant temperature of 30 C. 

 considerable canker developed. However, only one spot (on new growth) 

 occurred at the varying night temperatures. In other words, the eala- 

 mondin plant does not respond to so wide a temperature range for in- 

 fection as grapefruit. 



The citranges and the trifoliate orange plants differ from the grape- 

 fruit in their reaction to sudden changes. On the citrange, canker 

 developed at a constant temperature of 30 C. , while no spots whatever 

 were produced on the others, in spite of the fact that they were all in the 

 same condition when inoculated. Only a few spots occurred on a few" 

 of the trifoliate orange plants. However, the majority remained free 

 from canker at the varying temperatures. Thus, except on grapefruit 

 plants, a low night temperature has a tendency to inhibit infection and 

 the development of the disease. 



