210 THE BOOK OF NATURE STUDY 



upper end of the Broadbalk field, which had then been carrying 

 wheat for forty years in succession, was not harvested ; the crop 

 was allowed to stand and shed its seed without cultivation of 

 any kind. In the following season a fair quantity of wheat came 

 up on this part of the field, but gradually got weaker as the season 

 advanced and the weeds increased their hold on the land. 



" The wheat was still left to struggle on without cultivation, 

 and by the fourth season only three or four stunted plants could 

 be found, each carrying but one or two grains in the ear. With 

 these the wheat disappeared, and has never been seen again in 

 that part of the field/ ' 



From this example it may be understood how strenuous is 

 the competition existing in any meadow or hedge bottom, and 

 how, if the conditions become ever so slightly less favourable 

 to one species than to its neighbours it has very little chance of 

 surviving, except sparsely and locally where some accident restores 

 the balance in its favour. The differences which render one kind 

 of soil suitable to a given plant or cause it to be displaced by a 

 kindred species, are often very small indeed, so that it becomes 

 difficult to ascertain their exact nature. For example, in 

 most districts of England that are not too near the depredations 

 of large towns few flowers are so plentiful as the Primrose ; every 

 copse, every bankside, the edges of every ditch are full of them. 

 Yet here and there areas may be found where every condition 

 seems to be suitable, yet the Primrose is either entirely absent or 

 is only found in rare patches ; in the woods its habitual com- 

 panions, the Wood Anemone and the Bluebell, may be common 

 enough, and outside in the open fields Cowslips may be abundant, 

 but the Primrose itself is wanting. 



Many reasons may be advanced for this erratic distribution 

 but as yet the author has not found any one that is valid, 

 and similar cases occur everywhere. Always, however, the 

 element of competition is of more moment than any direct en- 

 couraging or injurious effect of the soil itself upon the plant. 

 To take an example, one of the most striking cases of local dis- 

 tribution of a British plant is the way the Yellow Horned Poppy 

 is confined to the otherwise almost bare shingle banks round our 

 coasts ; one would suppose it must love the salt spray and the 



