Winifred E. Bhexchley 19 



however, did not find the conditions suitable for germination, and there- 

 fore lay dormant. Many of them must have died oH, but some seeds 

 were apparently at such a nice condition of maturity that they were 

 able to establish equilibrium with their surroundings and so have 

 survived in a condition of latent life or dormancy until the present time, 

 30 years after they were shed. 



(4) New Zealand Field. 



This field was under grass from lUdi; till IDl.J. Prior to 1906 it was 

 under arable cultivation and in the autumn of 1915 it was again ploughed 

 up and is now cropped in the ordinary course of farm management. The 

 soil samples were taken before the grass was disturbed and two separate 

 sets of samples from four holes each were taken in August and September 

 1915. As the field is now cropped it has been possible to carry on obser- 

 vations of the arable weed flora as it appears in the field in order to make 

 comparisons with what happens under glasshouse conditions. 



The most striking feature of the New Zealand lists is the large number 

 of arable seedhngs that appeared in the greenhouse compared with those 

 obtained from Geescroft and Barn Field soils, the numbers being 457 and 

 334 respectively from the two New Zealand samples against 74 from 

 Geescroft and 12 from Barn Field grass. This is easily accounted for by 

 the relatively short time that New Zealand field had been down to grass, 

 as many seeds are known to be able easily to retain their vitality for over 

 10 years. On the other hand the number of true grassland plants was 

 less than in the other two cases, because the shorter period during which 

 the field was grassed over had not permitted such a large stock of unger- 

 minated, living seeds to accumulate. When all the seedlings exclusive of 

 grasses are considered together, it is seen that in the fields under con- 

 sideration the total number decreases as the length of time under grass 

 increases. This, however, must not be taken as a definite statement of 

 general application, because so nmch depends upon the initial state of 

 cultivation of the ground, the store of arable seeds originally in the soil, 

 and the particular soil condition which determines how long the seeds are 

 able to retain their vitahty. Probably, however, the statement would 

 approximately hold good under ordinary circumstances provided ample 

 allowance were made for individual and local variations. 



Altogether 16 arable species were derived from buried seeds, but 98 % 

 of the total number of seedlings were referable to nine of these species. 

 The number of seedlings of each individual species obtained from each 

 separate hole varied within wide limits, as from 1 to 36 with Papaver 



