{Decumaria harbara) and gray moss (Tillandsia usneoides) .f 

 One small spray of the gray moss has been found hanging over 

 Black Creek at Hartsville. 



As the nearest available information in regard to the rainfall 

 of Hartsville there are given below diagrams of the data for 

 Society Hill and Darlington : 



r 



CD 



H 

 O 



2 

















Jan. 

















Feb. 

















March 

















April 

















May 

















June 

















July 

















Aug". 

















Sept. 

















Oct. 

















Nov* 

















Dec. 



o 

 o 



rn 



< 



Jau. 



Feb. 



March 



April 



May 



June 



July 

 Aug-. 



Sept. 



Oct. 



Nov, 



Dec. 



Diagrams showing the mean annual rainfall for each month at Society Hill (for 

 the seventeen years preceding 1909) and for Darlington (for the thirteen years 

 preceding 1909). From the TJ. S. Weather Bureau reports. 



There is no doubt that one of the principal factors influencing 

 the distribution of species is the length of the growing season; 

 and this may be determined by the mean occurrence of the last 

 killing frost in spring and the first killing frost in fall. The 

 nearest stations to Hartsville for which this data is available are 

 Cheraw and Florence. For Cheraw the average date of the first 

 killing frost in fall is November 1st, and for the last killing frost 

 in spring is April 5th. For Florence the dates are November 

 7th and March 31st. This would give a growing season of 209 

 days for Cheraw and 220 days for Florence. Hartsville's growing 

 season would be nearer that of Cheraw's, say about 212 days. 



There are no humidity records for this section of South Caro- 

 lina, but I think there is no doubt that the humidity is less in the 

 vicinity of the sand hills than in any other part of the State. It 

 is almost certainly a difference in atmospheric humidity rather 

 than of temperature that accounts for the presence of the gray 

 moss (Tillandsia) at Darlington and its absence at Hartsville. 



tThe non-occurrence of these plants at Hartsville is supposed to be due 

 to a difference in climate. There are a number of others whose absence is 

 due to soil characters, e. g., certain shrubs and trees of the Pee Dee swamp. 



