129 



A careful study of the soil of s(;veral habitats cfjuliriiicd the 

 observation that D. annua grows normally with a water cf>ntent 

 of six per cent; when the i)ro[)ortion falls below this minimum 

 the plants die. The soil on analysis was found to contain 0.02 

 per cent nitrogen.* A mechanical analysis gave the following:! 



Per Cent 



Very fine sand 84.78 



Silt 8.12 



Clay 7-10 



u 



2 

 1 



Dec. Jan. 



Feb. Mar. 



Apr. May 



























































































































II 



h 



h 













1 





1, 



■ 



Fig. 2. Graph of rainfall for period of observation. 



The soil is therefore a fine sand, poor in nitrogen. Owing to the 

 impermeability of the subsoil, the overlying soil becomes water- 

 logged during heavy rains, or a series of showers, but its porous 

 sandy nature permits rapid drying. Figs, i and 2 show this 

 graphically. 



* Analysis made by Mr. M. T. Garret, senior student in agronomy, A. and M. 

 College. 



t Analysis made by Professor C. A. Wood, of the Department of Agronomy, 

 A. and M. College. 



