xxv.j CORN MILDEW AND BARBERRY BLIGHT. 199 



spores which burst and enter by germ tubes amongst the 

 tissues of the plants experimented upon, may possibly set 

 the latent germs of the fungus of corn mildew into activity. 

 In the case of the bunt of corn and of the potato disease 

 the presence of the fungus is clearly evident to experienced 

 observers long before the slightest trace of mycelial threads 

 can be detected by the microscope. We cannot help 

 thinking that more and better evidence of the supposed 

 genetic relationship between corn mildew and barberry 

 blight is much wanted. New illustrations are also wanted, 

 from new and unbiassed observers, of the germinating 

 pro-mycelium spores of Puccinia piercing the cuticle of 

 the barberry. We regret that we are unable to produce 

 an original illustration of this process of growth. A 

 single illustration of this phenomenon has been copied, 

 recopied, and copied again, sometimes with, but more often 

 without, acknowledgment, that one now almost feels angry 

 at the mere sight of the by far too familiar engraving. 



All low lying lands suffer most from mildew, and it is 

 said that elevated lands are next most seriously affected, 

 the intermediate positions being generally most free. This 

 fact is generally explained by the presence of mists in the 

 low lands, and clouds on the hilltops, the mists and clouds 

 being especially favourable to the development of Puccinia. 

 Mildew is commonly seen at its worst in placeswhere bushes 

 and trees abound, as these objects impede free currents of 

 air and aid fungus growth. Parasitic fungi which refuse 

 to grow in open gardens will often germinate and produce 

 disease at once if placed upon plants under bell-glasses. 

 The glass aids in keeping the air damp and motionless. 



We have ourselves observed corn mildew to develop with 

 great rapidity after rain in August, and we have sometimes 

 noticed the late sown wheat to be most affected. When 

 the ears are badly attacked the grain is not only greatly 

 impoverished and reduced to "skeleton grain," but it is 

 hardly possible to separate the seed from the husks. 



Mildew is said to be more frequent after crops of clover 



