10 Buried Weed Seeds 



declined to the sixth inch, below which depth very few seeds germinated, 

 although individuals appeared right down to the stiff clay of the twelfth 

 inch. Four arable seedlings put in an appearance, but it is possible that 

 they had been carried by birds or had been brought in on the feet of men 

 or horses and had then worked their way down into the soil. The distances 

 from the sampled area to the nearest arable field is considerable, and 

 neither charlock, fat hen nor orache have seeds that are at all well 

 adapted for wind dispersal. Fat hen and charlock seeds are heavy and 

 could not travel on the wind, and the orache remains enclosed in its 

 envelope, while the weight of the seed is such as to rendei' it improbable 

 that the wind plays any effective part in dispersing this weed, as the 

 envelope is not efficiently winged. The large number of Ajiiya seedlings 

 obtained from one hole six inches square is remarkable — 103 plants of 

 one species from such a small area being the second greatest number 

 obtained during the investigation. It is obvious that the sample must 

 have been taken from an area on which the plant is thoroughly well 

 established as the seeds were found right down to the tenth inch. The same 

 remark applies to Veronica Chamacdry^, though in this case the seeds were 

 more evenly distributed over three holes, while the fourth hole was utterly 

 barren of speedwell. Conopodiinn did not appear at all until the experi- 

 ment had been running for nearly a year, and it was very difficult to be 

 certain whether many of the tiny plants were genuine seedlings or whether 

 they had arisen from very small tubers which were already in the soil. 

 Even the smallest plants with obvious cotyledons developed their tubers 

 at an early stage, but probably the 25 plants observed included both 

 true seedlings and small older plants. The late appearance was probably 

 due to the fact that Conopodium is naturally a very early plant and Sis 

 it was later than the natural time of germination and growth when 

 the experiment was set up the seeds lay dormant for a year till the 

 usual growing period came round again. Centaurea nigra, again, gave 

 rise to a certain amount of doubt at first, but it is probable that nearly, 

 if not quite, all the 32 plants were true seedlings. In this case again 

 nearlvall the seedlings arose from one hole, indicating alocalaccumidation 

 of seeds. The leguminous plants were not very well represented, as only 

 19 individuals appeared. This may be because the hay is usually cut 

 before many of the clover seeds are ripe, so that the rdtimate effect of 

 haying on these species approximates somewhat to that of grazing, as 

 seen on the Common. 



