S86 WEEDS : GENERAL 



manufacture of food is possible, and the root and piece of stem 

 die of starvation. 



Mowing or cutting should commence in spring as soon as 

 young shoots appear, and should be repeated whenever fresh 

 shoots show themselves. It is useless to wait till summer or 

 autumn ;' the plants by that time have expanded their leaves, 

 and already prepared and stored a large amount of food in 

 their fleshy tap root and root-stock, or in their seeds. 



If instead of cutting above the cotyledons, annuals and 

 biennials are cut below them, across the hypocotyl or across 

 the root, the severed parts die almost immediately. The 

 formation of buds upon the roots of such plants rarely takes 

 place. Most species of thistle, cut below the "black knot" or 

 cotyledonous portion of the stem, as well as wild carrots, parsnip 

 and other plants, are thus readily exterminated, whereas cutting 

 above this point only increases the number of their shoots. 



With perennial plants it is usually different, as the under- 

 ground parts of these plants are often stems with buds upon 

 them and not roots. Once cutting these, either above or below 

 ground, is therefore useless, and even where the true root can be 

 severed from the stem the plants are not always destroyed, as 

 the roots of certain perennial weeds, notably docks and dande- 

 lions, readily give rise to adventitious buds. 



Ex. 271. — In summer dig up a dock root and cut it into pieces about an inch 

 long, and plant them in the ground or in a pot filled with garden soil. Do 

 the same with a young carrot or parsnip root, and observe the difference 

 between the pieces when dug up after a fortnight's growth. 



The cutting of weeds on arable land is generally accomplished 

 by means of the plough, hoe, cultivators and other implements, 

 and these can be made to exterminate annuals and biennials, 

 but perennials, such as couch, bindweed, coltsfoot, nettles and 

 docks, whose stems and buds are usually below ground, cannot 

 be destroyed by them. To merely cut such plants in this 

 manner only makes matters worse, as each piece of stem with its 



