LEAF AND SEEDLING DISEASES 181 
germinate directly by means of germ-tubes which infect 
healthy seedlings. 
An excess of moisture is conducive to both these diseases. 
Consequently good drainage is the most important inhibit- 
ing factor. When seed-beds are attacked it is advisable to 
allow the free play of air currents over the beds and to 
remove any obstructing objects. Spaulding (1908) has 
carried out trials with various powders and sprays. The 
most satisfactory powder was either (a) a finely powdered 
sulphur (that known as ‘ washed sulphur ’ is apparently the 
best), or (b) a mixture of powdered sulphate of copper 
(one part) and slowly slaked, very finely powdered lime (ten 
parts), the two being very thoroughly mixed together. The 
powders should be applied three or four days after the 
seedlings have come up, and from then onwards, after each 
shower, for about two weeks. A weak solution of sulphuric 
acid (1 oz. to 1 gallon of water) was found to be the most 
efficient spray. This solution may be applied with an 
ordinary sprinkling-can before the seeds are sown. 
