CHAPTER I. 



INTRODUCTION. 



IT is impossible to begin to work land under any system of 

 farming without immediately being confronted with the prob- 

 lem of weeds. Weeds are the inevitable corollaries of crops, 

 and much of the science of farming consists in the skilful use 

 of methods by which the weeds are kept in subjection. In 

 the ordinary course of events all vacant land tends to clothe 

 itself with vegetation, and soil that is artificially laid bare 

 during farming operations offers a situation that is most 

 favourable to the ingress of a native plant population. The 

 farmer's crops are more or less alien to the areas on which 

 they are grown, and consequently would havebut little chance 

 against the natural colonists if it were not for the assistance 

 rendered by husbandry methods. Weeds have thus a very 

 great practical and economic importance, and a right know- 

 ledge of their habits and distribution is a valuable asset. 

 Every farmer has a general knowledge of the worst weeds 

 that occur on his land, and usually knows how to deal 

 with them, but comparatively few have that special know- 

 ledge of the individual weeds which is necessary if the 

 more up-to-date and less-known methods of prevention and 

 eradication are to be successfully applied. The farmers of 

 this country are in possession of a vast amount of weed 

 lore, and much information is scattered up and down agri- 

 cultural literature, but hitherto very little attempt has been 

 made to bring together the facts and so to correlate them 

 that they form a complete whole, instead of being merely 

 disjointed scraps of knowledge of local interest and value 

 only. The field of inquiry is so large and the difficulty of 

 obtaining the necessary mass of information so great that it 

 is impossible to present anything like a perfect picture of the 

 weed problem, but the aim of the present book is to sketch a 

 preliminary outline from the facts that are already available, 

 in the hope that at some future date it may be possible, 



