HARM DONE BY WEEDS 13 



for its own uses. Such weeds as these may do great 

 damage, even killing extensive areas of the crop on 

 which the farmer may be largely depending. The two 

 most serious agricultural parasitic weeds are Dodder 

 and Broom-rape, both of which attack red clover 

 (Trifolium pratense). Other weeds, as Yellow Rattle 

 (Rhinanthus Crista-galli), Lousewort (Pedicular is), Eye- 

 bright (Euphrasia officinalis), and a few others, are semi- 

 parasitic on the roots of grasses. (See Chap. VII.) 



(/) Some Weeds are Poisonous, either to man or to 

 farm live stock, and, as such, are to be destroyed. 

 Numerous plants have from time to time been re- 

 corded as poisonous, and have frequently proved fatal. 

 (See Chap. VIII.) 



In other cases, although not directly harmful to 

 stock, weeds may taint the milk, and consequently the 

 butter made from it, of cows which have fed upon 

 them, thus lowering the market value of the produce or 

 rendering it distasteful for home consumption. Such 

 weeds as Garlic (Allium sp.), Garlic Mustard (Alliaria 

 officinalis), Ivy (Hedera), Ranunculus acris, Chamomile 

 (Anthemis), and others, are harmful in this way to the 

 dairy farmer. 



(g) Climbing and Binding Weeds drag down the Cultivated 

 Crop and prevent proper Growth. This may be well seen 

 in the case of the Bindweeds (Convolvulus arvensis, C. 

 septum, and Polygonum Convolvulus), which twine them- 

 selves round bush fruit-trees, cereals, and many garden 

 crops. When they once gain a footing they are 

 difficult to eradicate, and may do much damage. 

 Wild Vetches, Cleavers, &c., may by sheer weight 

 break down corn crops. Traveller's Joy (Clematis 

 Vitalba), Bryony (Bryonia dioica), and Honeysuckle 

 (Lonicera Periclymenum) are climbing hedge weeds. 



(h) The Commercial Value of Agricultural Seeds is much 



