Winifred E. Brknchlev 5 



capacity was as high (87 %) after ten years as after one year, whereas in 

 dry storage it was reduced to 82 % in one year and to 24 % in 10 years. 



In these two cases it is evident that the conditions of burial are more 

 conducive to the retention of germinating capacity than are those of dry 

 storage. This provides a connecting hnk between the popular idea that 

 charlock seeds can remain dormant in the soil for many years and the 

 results obtained by the British Association Committee, in which species 

 of Brassica kept in dry storage lost their power of germination in a very 

 few years {B. napvs eight years. B. rapa eight years, B. olemcea three 

 years). 



Dorph-Petersen also tested the effect of depth of burial by placing 

 weed seeds 3 ins., 6 ins. and 12 ins. below the surface. The trials lasted for 

 six years and showed that seeds placed at the greatest depths retained 

 their germinating capacity best. The seeds of cultivated plants, especi- 

 ally grasses, died much more quicklv in soil than did the related weed 

 seeds. 



Since August, 1915, experiments have been carried on at Rothamsted 

 to test the power of sermination of seeds buried in the soil under natural 

 conditions at different depths, without any artilicial placing or burial of 

 seeds. To this end a number of samples were taken from different fields 

 of known history by means of a sampling iron, 6 ins. by 6 ins. by 9 ins. 

 This was driven into the ground, and the soil was carefully removed inch 

 by inch, each inch being placed in a new paper bag and carefully labelled 

 with the depth from which it was taken. The iron was driven far enough 

 in to permit of sampling to a depth of 12 ins., and special precautions 

 were taken that no crumbs of soil from the surrounding areas fell inside 

 the sampling iron. The samples were then placed in clean sterilised pans 

 or boxes in a greenhouse, kept watered, and left undisturbed for a time. 

 The lower inches were chiefly heavy clay, which was broken up into 

 small pieces by the fingers. After some months the sticky clay began 

 to break down and disintegrate to some extent. Seeds soon began to 

 germinate, and as soon as they were large enough to recognise they 

 were noted and removed from the soil. Special care was taken that no 

 plants were allowed to fruit and ripen seeds in the pans, Occasionally 

 when the seedhngs had been removed the soil was stirred and cut up 

 with a knife. To avoid any danger of contaminating the samples, before 

 the soil in anv one box was interfered with all the surrounding boxes 

 were covered with slates. As the boxes and jjans were under cover in a 

 greenhouse there was little danger of contamination by seeds carried on 



