THE CLOVERS— RED AND COWGRASS. 105 



inferior samples to vend take care to keep them out of 

 the reach of testing stations. The Clover Dodder (Cus- 

 cuta trifolii) is the most terrible enemy of the clover 

 plant. It is sown with the seed, and develops simul- 

 taneously ; it winds its hair-like stems round the clover 

 plant (as explained in an earlier chapter of this work), 

 and fixes itself on to it by means of suckers, which 

 extract the sap from the clover plant. The roots, which 

 the Dodder possesses in the early stages of its growth, 

 wither after a while, and then the parasite is altogether 

 dependent on the sap it draws from the clover plant, 

 in consequence of which the latter wastes and perishes. 



Clover Sickness. — The phenomenon called Clover Sick- 

 ness arises, according to Liebig, from the deficiency of 

 miaeral matter in the subsoil, which opinion is sustained 

 by Kutzleb, whose experiments have demonstrated that 

 it is brought about by the want of a sufiScient propor- 

 tion of potash in a soluble state in the, subsoil. On 

 soils which, by their composition, are not suitable to the 

 culture of this plant, it should not be planted at shorter 

 intervals than from nine to twelve years — if a satisfac- 

 tory crop is to be expected. Experience has also proved 

 that Eed Clover is more likely to fail when it succeeds a 

 plant of the same family, such as the Pea, Bean, Vetch, 

 Trifolium iiicarnatum, &e. &c. 



Mami/ring. — At Eothamsted ammonia salts had the 

 effect of eliminating this plant from the various plots 

 to which they were applied, whether in conjunction 

 with mineral manures or alone. Nitrate of soda also 

 diminished the growth. 



