62 



Lloyd and Tracy : The insular Flora 



Climate 



The data here used have been derived from the Annual Re- 

 port of the Monthly Weather Review for the past eight years, 

 the New Orleans data being used. 



Temperature 



The mean annual temperature of the Delta is near 2i.i°C, 

 while that of Ocracoke is 16.3 C, a mean difference of nearly 

 4.9 C. (9.0 F.). The maximum temperature is 36. 1 ° C. (97°° F0» 

 and the minimum — 16. 1 °C. (7.0 F.),the lowest and highest points 

 registered in eight years. In this regard the two places differ but 



b 



a 



Fig. 1. Curves showing the mean monthly temperatures of Hatteras (*-<*) all( 

 the Mississippi Delta (^-^). 



little. As the accompanying curves (Fig. i) will show, however, 

 the general temperature is higher, and the growing season longer, 

 at the more southern point, as shown by the more rapid rise of the 

 curve after the middle of February, and the steady maintenance of 

 an effective growing temperature in the earlier and later months of 

 the growing season. And in this lies the chief climatic difference 

 of physiological moment between the two places here under con- 

 sideration. 



One might readily suspect that the meteorological observations 

 made at New Orleans would show some variation from the condi- 

 tions found on the small islands of the Delta and adjacent parts. 

 A comparison of data taken at New Orleans and the rather frag' 



