148 



DISEASES OF CROPS. 



ated by the rotting of the root-nodules. These spores 

 retain their vitality for months,^ and are then capable of 

 attacking the new seedlings planted in such soils. The 

 spores are easily disseminated by such agencies as air, 

 soils, and streams. Ustilago cucumeris produces a diseased 

 condition of the whole plant. 



Prevention. — (1) Avoid growing cucumber plants in the 

 same soil season after season. (2) Sow only good healthy 



Fig. 50.- 



-Spobk Formation. 



X 713. 



Cure. — Water the infested plants with a 4 per cent, 

 solution of iron sulphate. The iron sulphate completely 

 destroys the fungus, but does not injure the host-plant.' 

 Mr. E. F. Crocker (already mentioned) has been successful 

 in destroying the said fungus by using iron sulphate. He 

 wrote the author as follows : — " I planted the present house 



1 Proceedings Royal Society, Edinburgh, vol. xv. p. 410. 



2 Ibid., p. 409. 



