Winifred E. Brenchley 25 



been Q;rassed over for 10 years vast numbers of arable seeds retain their 

 vitality and are ready to spring up and dominate the situation at the first 

 favourable opportunity. When once the arable weeds have their oppor- 

 tunity the true grassland plants have little chance and make a very poor 

 show a few months after ploughing. 



C. Arable Land. 

 (1) Long Hoos. 



This field has been and is under ordinary farm management, so that 

 the weed seeds that germinated during the experiment had not been in- 

 fluenced in number or condition by any period during which the land had 

 been under grass. Consequently the results indicate the normal state of 

 affairs in land which is cultivated under rotation cropping in which 

 experimental methods have played no part. The number of seedling.s 

 obtained was enormous — although only two holes were sampled, repre- 

 senting an area of | sq. foot, no less than 782 arable weed seeds, repre- 

 senting over 68 millions per acre, germinated during the sixteen months 

 that the experiment had been carried on. Up to the previous December 

 (1916) .524 seedlings had appeared, so that an additional 2.58 seeds started 

 into growth during the second season. These numbers are very large, being 

 four times as many as were obtained from a similar area over a longer 

 period from New Zealand field, which had been under grass for 10 years. 

 The amount of possible competitive damage that can be done by weeds 

 in the absence of efficient cultivation is strongly emphasized by these 

 results, as if the weeds were left undisturbed to germinate and fight their 

 own mutual battle, the introduced crop plants would have little chance 

 in the fray. 



The number of arable weed species that appeared were greater than in 

 any other set of samples that were taken. Arenaria serpyllifolia, Alche- 

 milla arvensis, Veronica Tournefortii, and Matricaria inodora were the 

 most abundant, contributing altogether 70 % of the total, so that they 

 are evidently very widely distributed over the field. Anagallis arvensis, 

 Galium sp., Pnlygorinm, Convolvulus, Sonchis asper and Caucalis sp. 

 were very scarce, indicating that these species are more or less local and 

 occa.sional in their distribiition. It is noticeable that though Atriplex 

 jjatnla is one of the weeds that is most resi.stant to long burial on this 

 soil, yet it is not one of the most abundant species, and apparently its 

 distribution is somewhat irregular, as the numbers obtained from the two 

 holes vary so widely. 



