GRAMINEOUS CROPS. 127 



In the spring they germinate on decaying gramineous 

 plants, giving rise to a short pro-mycelium. The pro- 

 mycelium produces yellow-coloured spores, which germi- 

 nate on damp surfaces. These yellow-coloured spores 

 are said to ultimately give rise to an ^^idium fungus 

 on certain members of the Boraginacece [e.g. Symphytum 

 asperrimum (prickly comfrey), Symphytum officinale 

 (common comfrey), etc.], which also produces spores. The 

 JEcidium spores (according to the late Dr. De Baryi and 

 other authorities) reproduce (on certain cereals and 

 grasses) the Uredo, or the "rust " stage, of P. ruUgo-vera. 



This fungus infests wheat, barley, rye, as well as 

 certain grasses. 



Prevention. — (1) A good system of land drainage lessens 

 the attacks of this fungus. (2) According to Mr. W. G. 

 Smith, F.L.S., " It is now generally accepted as a' fact 

 amongst practical men, that after dressing the land with 

 farmyard manure and nitrate of soda mildew often puts 

 in a strong appearance ; but after mineral -manures, bone 

 superphosphate, and bone meal drilled with the seed, 

 rust and mildew are much less apparent. There can be 

 no doubt that farmyard manure has a tendency to produce 

 a gross soft growth in corn which is suitable for fungi, 

 and that mineral manures, on the contrary, have a ten- 

 dency to produce a firm, stiff growth unsuited for rust and 

 mildew." (3) Seeds from infested plants should not be 

 drilled. (4) It would be well for farmers to burn mil- 

 dewed straws, as this material (when used as litter) is a 

 suitable medium for the teleutospores to hibernate in. 

 The author has experimentally shown that certain fungal 

 spores are capable of hibernating for months, in farmyard 



' Neue Untersuchungen uber Uredineen, ii. (1866). 



