xxv.] CORN MILDEW AND BARBERRY BLIGHT. 205 



days as requisite for a closely-allied species, Gardeners' 

 Chronicle, 28th October 1882. 



The experiments were varied in many ways, and 

 if Professor Farlow' s full reports of the carefully conducted 

 experiments are examined, it will be seen that heteroecism, 

 as regards the American species of Podisoma and Rcestelia, 

 completely breaks down at every point. Out of nineteen 

 experiments no less than fourteen were without result ; 

 when results followed they were contradictory, and 

 sometimes, as Professor Farlow remarks, " desperate." 

 In 1879 Professor Farlow was absent, but in 1880 he 

 returned and made further experiments : these were 

 invariably without result. 



We have shown in this work that Puccinia (mildew) 

 and dEcidium (blight) are potentially perennial, heredit- 

 ary, and always either in an active or passive state 

 in the juices of the plants invaded. Professor Farlow 

 adverts to the same fact as regards the American fungi, 

 and suggests that the appearance of the spermogonia 

 was in consequence of the presence beforehand, in the 

 leaves, of the mycelium of some Rcestelia which was made 

 to develop by the moist condition in which it was placed. 

 " I am strongly inclined," writes Professor Farlow, " to 

 favour this view." He further states that, unless he is 

 mistaken, he has seen the Roestelia state earlier in the 

 season than the Podisoma and so, instead of following, as 

 stated by Oersted, it has preceded, the Podisoma. He 

 concludes by saying : " Another important fact is to ascer- 

 tain how many of our Rwstelice are perennial. This at 

 least appears to be the case with R. aurantiaca, Pk. If it 

 should be shown that several of our Rcestelice are perennial, 

 a fact true of our Gymnosporangia (Podisoma), and to grow 

 in regions remote from Juniperus and Cupressus, then one 

 could not help feeling that any connection between the 

 two genera was probably accidental rather than genetic." 



The amount of confusion that exists in books as to the 

 host plants, and second conditions of the so-called heterce- 



