CHAPTER VII 



PARASITIC PLANTS 



A considerable number of weeds are parasitic or semi- 

 parasitic in character, subsisting wholly or in part upon 

 the food material elaborated by the " host " plant for 

 its own use. One or two of these parasites are serious 

 pests, and frequently do much damage. 



CONVOLVULACE.E 



Dodder (Cuscuta sp.) is one of the most troublesome 

 of weed pests with which the farmer has to contend, 

 chiefly on account of the damage it does to red clover. 

 Many species of Dodder are harmful, and some eighty 

 species are known to science, several occurring in 

 Britain. These parasites are mostly annuals, growing 

 from seed sown with farm seeds or self-sown in a 

 former year, and they subsist on plants of a higher 

 order. 



The various species of Dodder closely resemble one 

 another in their life history and manner of growth. 

 The seed contains a simple, thread-like embryo which 

 is coiled spirally round the fleshy albumen, and the 

 radicle end is thickened. A damp season appears 

 most suited to the requirements of the Dodder seed, 

 and at a proper temperature the seed germinates in 

 five to eight days. The thread-like coil gradually un- 



