78 WEEDS OF FARM LAND 



(/) Worms, which help to bury seeds 4 or 5 feet, especially 

 smooth or rolling seeds like those of charlock, clovers, 

 thistle and broom. 



(g) Sun and earth cracks, in which, however, most seeds 

 perish. 



(h) Rock cracks. 



Other means may suggest themselves, but the above list is 

 sufficiently comprehensive to indicate the -great variety of 

 ways in which seeds may be carried underground to consider- 

 able depths. 



When once burial has taken place the conditions determine 

 whether the seeds lie dormant or start into premature growth 

 and perish. It seems probable that most of the seeds in the 

 top few inches of soil are in the presence of sufficient water, 

 air and warmth to enable them to germinate, and it then 

 depends upon the vigour of the seedlings and the relative 

 depth of burial whether the young plant can reach the surface 

 or whether it perishes ignominiously, stifled at birth. The 

 deeper buried seeds, however, seem to be able to set up some 

 condition of equilibrium with their surroundings, and instead 

 of germinating many of them lie dormant, awaiting some turn 

 of events that will bring them into more favourable circum- 

 stances. Waldron x buried seed for several years and then 

 tried to germinate them, and found that the deeper buried 

 seeds, up to a depth of 10 inches, were the better preserved. 

 As years go on numbers of the buried seeds rot and perish 

 in other ways, but a certain number survive for long periods 

 of time. Very definite evidence that this is the case is pro- 

 vided by the crops of weeds that spring up when methods of 

 cultivation are altered. 



An instance has recently occurred in Cumberland. Forty 

 acres of land covered with gorse and heath were broken up in 

 1893 and kept clean under arable cultivation for over ten 

 years. Between 1904-06 the land was laid down to grass, 

 and gorse seedlings soon appeared. These were stubbed out 

 without being allowed to seed and no more appeared on the 

 pasture. In the winter 1917-18 the area was ploughed up 

 and sown with oats, and gorse seedlings soon reappeared. 

 At harvest time they were abundant in the stubble, being 

 most plentiful where the gorse was originally thickest. These 



1 Waldron, L. R. (1904), " Vitality and Growth of Buried Weed Seeds," 

 North Dakota Agric. Coll. Bull., No. 62. Also see Munerati, O., and Zapparoli, 

 T. V. (1913), Le Stazioni spenmentali agrarie italiane, Vol. XLVI, pp. 347-371. 



