26 



transferred from the barberry to the corn."* Professor Henslow 

 was the next authority upon this subject, who confirmed Sir Joseph 

 Banks' conclusions, and iirst propounded the theory, afterwards 

 confirmed by Tulasne, that the yellowish rust which appears in 

 summer, and the black mildew which comes later, are identical. 

 Professor Henslow also gave much credence to the connection 

 between the barberry and the wheat mildew, but did not much ad- 

 vance the knowledge of this part of the subject beyond Sir Joseph 

 -Banks' " possible " connection. f But little was added to the in- 

 formation as to mildew until 1865, when De Bary published the 

 results of experiments practically demonstrating that an 

 JEcidmm,^ or a stage of a fungus known as dEcidium berberidis, 

 found on the barberry tree, is the origin of the wheat mildew, 

 or, in other words, the first stage in the life of the mildew. 

 This explained the mystery. All attempts to produce the early 

 stage of the mildew, called " rust," upon wheat plants by means 

 of the black spores, or teleutospores, had utterly failed, and 

 De Bary proved that wheat plants can be affected by the 

 ^Ecidiospores, or spores direct from the barberry tree, and that 

 the teleutospores germinate upon and infect the barberry. 

 De Bary's discovery was not accepted at once, but now it is 

 generally recognised as the solution of the difficult question as to 

 the first cause of wheat mildew. 



There is, however, a disposition to believe that the ^Ecidium 

 may have another host plant, at least in other climates, and in 

 some circumstances ; this will be dealt with later on. 



THE LIFE HISTORY OF THE FUNGUS. 



The wheat mildew, Puccinia graminis, belongs to the group 

 of fungi, termed Uredineae, which, as De Bary points out, are 

 all parasites on livng plants.|| Some of the -species of this group 

 go through the various stages of their existence upon our host 

 plants, being styled autcecious. Others are hetercecious, and 

 pass from one host to a different host in their various stages of 

 development. l j uccinia graminis is a typical instance of this, 

 as in its ^Ecidium form it lives upon varieties of Berberis ; and 

 only upon corn plants and grasses, first, in its uredospore, and 

 then in its teleutospore condition. 



Those who have carefully noticed barberry bushes in the 



A Short Account of the Cause of the Diseases in Corn, culled by farmers 

 the Blight, tin- MiltJcw, and the Rust, by Sir Joseph Banks, Bart. P.R.'s. 



f On ih>. Dlxpa*f.n of Wheat, by Professor Henslow, M.A. Journal of the 

 Royal Agricultural Society of England, vol. ii., p. 1, 1841. 



J Literally, a small house. De Bary explains it as "in the Uredinese 

 a cup-shaped envelope and a bymenium occupying the bottom of the cup' 

 from the basidium of which spores, secidiospores, are serially and succes- 

 sively abjointed." 



Neue Untersuchunijen iiber Uredineen. De Bary, Monatsbericht der 

 Berlin Akademie, 1865. 



|| Comparative Morphology and Biology of 'the Fungi. Mycetozoa, and 

 Bacteria, by A. De Bary. 



