188 NATURE STUDY AND AGRICULTURE 
we should develop and use a strain of seed that resists the 
attack of the disease. 
Potato scab shows itself on the surface of the potato in 
the form of irregular, rough patches. It is caused by a fungus 
that grows from spores on the seed potato or in the ground. 
(1) As already explained, to prevent infection from the seed 
potatoes we may soak them in a formaldehyde solution and 
kill the spores. (2) After potatoes have been raised in the 
Younc FLAx PLANTS 
Wilted, due to early attack 
of the wilt fungus from flax- 
sick soil. (After Bolley.) Potato ScAaB 
same ground a number of years so that the soil has become 
infected with the scab, some other crop should be grown 
on this land for a period of years and potatoes raised else- 
where. 
Bean-pod spot manifests itself in the form of brownish or 
blackish patches on the pods of beans, which injure them 
greatly. Seeds from such pods are apt to contain the fungus, 
and if planted, this will infect the seedlings and in due time 
the pods. The best method of prevention, therefore, is to 
avoid planting infected seeds. Spraying the plants with Bor- 
