8o 



WEEDS OF FARM LAND 



arable fields, even the one that had been under grass for fifty- 

 eight years, yielded arable weeds in such numbers as to pre- 

 clude the possibility of accidental infection after the land was 

 grassed over. One is therefore forced to the conclusion that 

 the seeds had lain dormant throughout the years. 



The grand total of typical arable weeds obtained from the 

 samples are given in the following table : 



The above table shows that after ten years of burial very 

 large numbers of weed seeds are still alive and capable of 

 springing into activity as soon as circumstances are favourable. 

 The number decreases with time, but even after thirty years 

 or more it is still great, as 74 seeds from an area I foot 

 square by I foot deep implies a surprisingly large total per 

 acre. Still longer periods of burial fail to destroy all the 

 seeds, though the number of live seeds decreases considerably. 

 The greater number of the arable weed seeds were found 

 several inches below the surface, and many of them were rest- 

 ing as far down as twelve inches. The actual number found 

 at the different depths are shown in the following table : 



Total Numbers of Arable Weed Seeds from Different Depths, 



