22 DISEASES OF CBOPS. 



Dodder rarely produces seed in Great Britain, but its 

 stems are often perennial. " In the early stage of its 

 existence dodder is not a parasite, for after the germina- 

 tion of its seed, it grows like an ordinary plant, sending 

 its roots down into the soil, from which it draws its 

 nourishment. This state of existence, however, is short, 

 for unless it meets with some congenial plant to which it 

 can attach itself, and from which it can draw nourish- 

 ment, it withers and dies." 



Prevention. — (1) Dodder grows upon other plants be- 

 sides clover : viz. — nettles, broom, furze, yellow bedstraw, 

 sow-thistles, etc. These should be removed from all lands 

 growing clover. (2) Continental clover seeds often con- 

 tain those of dodder. The latter should be sifted away 

 as far as possible. 



Cure. — (1) " The Continental remedy is to dissolve 

 iron sulphate in water, at the rate of 1 lb. to the gallon, 

 and water the infected spots with the solution. This 

 kUls the dodder and leaves the clover uninjured." (2) 

 " Carefully collect and burn all the patches of dodder 

 after the crop has been removed, and then give the field 

 a good clean fallow. All such operations as harrowing 

 and raking do harm, for instead of extirpating the dodder, 

 they only further the mischief, as it is well known that if 

 the dodder is cut into a hundred pieces, each piece will 

 go on growing and become a separate plant." 



The Clover Mildew {Peronospora trifoliorum, 

 Fig. 6) is a fungoid growth, and is one of the causes of 

 " clover sickness." P. trifoliorum grows within the 

 leaves of. the clover plant, although it sends out aerial 

 branches (conidiophores) through the stomata (openings) 

 which are found largely on the under surface of the leaves 

 (Fig. 6 a). The conidiophores bear oval spores (conidia. 



