VEGETAJiLE AND FIELD CROPS 



297 



Damping off may occur upon seed beds. The plants are 

 attacked when very young, and death may result before 



Fig. 129. — Tobacco roots showing effect of thielaviose. After Gilbert. 



they attain a height of more than 5-10 mm. In other cases 

 of milder attack the roots alone are invaded and the plants 



