EXTERMINATION OF WEEDS 585 



often worse than useless, it is necessary to explain the effect of 

 cutting various plants in different ways. When the stem of any 

 plant is mown or chopped off above the cotyledons, the plant for 

 the time being is prevented from flowering and seeding, and the 

 cut-off portion usually withers and dies rapidly when exposed to 

 the drying action of the sun and air. The portion of Stem still 

 attached to the growing root, however, suffers little, and the 

 dormant buds in the axils of the cotyledons and lower leaves of 

 the plant receive water and nutrient materials from the uninjured 

 root and piece of stem which stimulate them to grow. Thus 

 cutting off the stem of a plant frequently results in the subse- 

 quent appearance of many stems to take the place of the one 

 removed, their vigour and number depending on the species of 

 plant, its age, and other points. 



An annual plant cut in spring in the above manner soon after 

 germination is very much weakened, and a repetition later as 

 soon as the lateral buds have developed into stems exhausts the 

 plant and generally kills it. 



Biennials in their first year of growth have a shortened stem, 

 and cannot usually be mown with a scythe ; if cut, however, with 

 other implements above the cotyledons when still young, they are 

 as readily weakened as annuals. In late summer or autumn, after 

 one season's growth, biennials and perennials have their short 

 stem and root stored with food, and at that period of their life 

 are very little injured by cutting above the cotyledons. They 

 subsequently send up several vigorous shoots instead of 

 one. 



Repeated cutting, however, ultimately kills all plants- 

 annuals, biennials and perennials alike — by depriving them of 

 their organs of 'assimilation,' and thus preventing them from 

 making good their loss. Stored food becomes used up by the 

 repeated development of buds into stems and leaves, and if 

 the latter are removed as fast as they are formed, no further 



