LIMITING FACTORS OF GROWTH IN FLORIDA 



155 



China, and the average for six points in Florida* for a long period 

 of years is shown below: 



It is evident at a glance that the Canton climate in January, 

 1919, was much colder than the average of south Florida points, 

 and especially the mean maximum temperature was much lower. 

 The thermometric records do not fully show the difference between 

 South China and Florida, since the bright sunshine (50 to 60 per 

 cent or more of the total possible) of the south Florida winter 

 would heat the leaves, buds, and twigs of a tree to a higher tem- 

 perature than that of the air, while nothing of the kind happens 

 during cloudy weather in China. 



The records reprinted above show that at Canton, China, 

 during the eleven days from January 8 to 18, 1919, the minimum 

 temperatures were above 12.3 Cent. (55.1 Fahr.), the daily mean 

 temperatures were above 15.7 Cent. (61.3 Fahr.), and the maxi- 

 mum temperatures were above 19.1 Cent. (66.4 Fahr.), the hot- 

 test day being the loth with the minimum 18.4 Cent. (66.1 Fahr.), 

 the mean 23.2 Cent. (73.7 Fahr.), and the maximum 27.9 Cent. 

 (82.3 Fahr.). Probably the growth on the lychee trees observed 

 about January 25 resulted from this spell of warm weather. 



Such a moderate warm spell as this is sure to occur during 

 every Florida winter, with the added stimulus of bright sunshine 

 half or more of the time. 



If a surmise be ventured, I would place the zero point of 

 growth of the lychee, in the light of the facts recorded above, 

 between 16 Cent, and 18 Cent, (about 6o-65 Fahr.). It is 

 clear that the lychee has a very low degree of winter dormancy. 



The fact that the lychee was growing at Canton in the last 

 week of January, 1919, in spite of prolonged cloudy weather and 

 low maximum and mean temperatures, proves that it is able to 



*Henry, Alfred J. Climatology of the United States. Weather Bulletin B. ( Washington 

 D. C., igo6, pp. 352-361. 



