152 What is a Weed? 



grow by competing with it for space, and robbing 

 it of sunlight and air, and of the food and moisture 

 in the soil. But the curious class of parasites, 

 of which several species work considerable mischief 

 to English agriculture, make a more direct attack 

 upon the plant by draining it of its own vital 

 juices. The most familiar example of a parasite 

 is the mistletoe. This ranks as a pest in many 

 old orchards, though it has an independent market 

 value which makes it worth the while of the provi- 

 dent French farmer to export it in large quantities 

 to this country at Christmastide. Less known to 

 the world at large, though of greater importance 

 to the farmer, are the various species of broom- 

 rape and dodder. The dodder's thread-like stems 

 and small pink or white clusters of blossom are most 

 familiar as a parasite upon furze-bushes, in which 

 situation they are no special concern either of the 

 farmer or the gardener. But one species will 

 attack the China aster, while the vegetable garden 

 may also be infested. The lesser dodder, of which 

 the stems attach themselves to furze, thyme, and 

 heather, is believed to be a separate species from 

 the parasite upon clover, which is often a trouble- 

 some pest, and is chiefly propagated by sowing 

 impure clover seed from abroad. Unlike the mistle- 

 toe, which is sown upon the boughs of trees by birds, 

 the dodder must find its seed-bed in the soil, and to 

 this slight extent it is a non-parasitic plant. But 

 as soon as the growing stem can attach itself to 

 a victim it breaks its link with earth, and hence- 

 forth subsists wholly as a parasite. 



