xxv.] CORN MILDEW AND BARBERRY BLIGHT. 201 



examples of corn have a strong and inherited predisposition 

 for mildew ; therefore predisposed examples should be 

 struck out and no seed gathered from them. Especial care 

 should be taken in the rigorous selection of seed from white 

 wheats, which are notoriously more subject to mildew than 

 red, probably because the latter are naturally more robust. 

 If seed merchants would guarantee that the seed corn they 

 sell is taken solely from corn free from mildew, in the 

 course of years the attacks and consequent losses from this 

 pest would be considerably lessened. Mildew is every 

 year so common in our fields simply, as we think, because 

 the disease is planted with the grain. Old corn stubble 

 should not be left too long in the fields. Some corn 

 growers say that a top dressing of salt has a tendency to 

 lessen or prevent mildew. 



Mildewed straw is bad when used as food for stock in 

 chaff, and the inferior grain is hardly fit for pigs. The 

 straw is more commonly used as litter in stables. In this 

 position the spores of the Puccinia remain uninjured, for 

 neither warmth, frost, wet, or dryness materially affect 

 the vitality of the resting -spores of the fungus of corn 

 mildew. They are so small that no amount of treading 

 from horses, herds, or flocks injures them. The warmth 

 and dampness of the stable floor in every way suits them, 

 and they are frequently taken from this position, full of 

 life, and at once thrown on to the fields in the saturated 

 straw. If the spores are consumed with food by animals, 

 their passage through the alimentary canal does not injure 

 them. The disease is probably, as we think, propagated 

 by the mildewed straw being used as manure, and by the 

 germinating resting-spores of the fungus of corn mildew 

 infecting the first young leaves of the corn. 



Mildewed straw should be destroyed, because the Puc- 

 cinia, with its myriads of resting-spores, is in this material. 

 We have shown that these resting-spores germinate in the 

 spring and early summer at the exact time when rust, 

 which is the early state of mildew, first appears. Whether 



